# Fatal error since installed Mautic API **URL:** \ **Category:** Product Support\ **Tags:** mautic-4\ **Created:** [December 18, 2021, 8:09pm UTC](https://forum.mautic.org/t/fatal-error-since-installed-mautic-api/22071 "2021-12-18T20:09:01Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![nickbm](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/nickbm/32/6488_2.png) [@nickbm](https://forum.mautic.org/u/nickbm)\ **Post date:** [December 18, 2021, 8:09pm UTC](https://forum.mautic.org/t/fatal-error-since-installed-mautic-api/22071/1 "2021-12-18T20:09:02Z")
**Your software** My Mautic version is: 4.1.0 My PHP version is: 7.4.27 My Database type and version is: 8.0.27 **Your problem** My problem is: I run composer require mautic/api-library It run successfully, but since then I’m getting this error on the main Mautir URL These errors are showing in the log: ` **Fatal error** : Uncaught Error: Class 'Mautic\CoreBundle\ErrorHandler\ErrorHandler' not found in D:\inetpub\vhosts\ ******.com\wwwroot\m.******.com\public\index.php:22 Stack trace: #0 {main} thrown in **D:\inetpub\vhosts\******.com\wwwroot\m. ******.com\public\index.php** on line **22** ` Steps I have tried to fix the problem: ---
**Author:** ![nickbm](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/nickbm/32/6488_2.png) [@nickbm](https://forum.mautic.org/u/nickbm)\ **Post date:** [December 18, 2021, 8:13pm UTC](https://forum.mautic.org/t/fatal-error-since-installed-mautic-api/22071/2 "2021-12-18T20:13:49Z")
This is the log: D:\inetpub\vhosts\*\*\*\*\*.com\wwwroot\m.\*\*\*\*\*.com\public\>composer require mautic/api-library Using version ^3.0 for mautic/api-library ./composer.json has been created Running composer update mautic/api-library Loading composer repositories with package information Updating dependencies Lock file operations: 2 installs, 0 updates, 0 removals - Locking mautic/api-library (3.0.0) - Locking psr/log (1.1.4) Writing lock file Installing dependencies from lock file (including require-dev) Package operations: 1 install, 0 updates, 182 removals - Downloading mautic/api-library (3.0.0) - Removing willdurand/negotiation (3.0.0) - Removing willdurand/jsonp-callback-validator (v1.1.0) - Removing voku/stop-words (2.0.1) - Removing voku/portable-ascii (1.5.6) - Removing twilio/sdk (5.42.2) - Removing twig/twig (v3.3.2) - Removing tightenco/collect (v8.34.0) - Removing theofidry/psysh-bundle (4.4.0) - Removing symfony/yaml (v4.4.26) - Removing symfony/var-exporter (v5.3.3) - Removing symfony/var-dumper (v4.4.26) - Removing symfony/validator (v4.4.26) - Removing symfony/twig-bundle (v4.4.26) - Removing symfony/twig-bridge (v4.4.26) - Removing symfony/translation-contracts (v2.4.0) - Removing symfony/translation (v4.4.26) - Removing symfony/templating (v4.4.25) - Removing symfony/swiftmailer-bundle (v3.5.2) - Removing symfony/string (v5.3.3) - Removing symfony/stopwatch (v4.4.25) - Removing symfony/service-contracts (v2.4.0) - Removing symfony/security-bundle (v4.4.26) - Removing symfony/security-acl (v3.0.4) - Removing symfony/security (v4.4.26) - Removing symfony/routing (v4.4.25) - Removing symfony/property-access (v4.4.25) - Removing symfony/process (v4.4.26) - Removing symfony/polyfill-php81 (v1.23.0) - Removing symfony/polyfill-php80 (v1.23.0) - Removing symfony/polyfill-php74 (v1.23.0) - Removing symfony/polyfill-php73 (v1.23.0) - Removing symfony/polyfill-php72 (v1.23.0) - Removing symfony/polyfill-mbstring (v1.23.0) - Removing symfony/polyfill-intl-normalizer (v1.23.0) - Removing symfony/polyfill-intl-idn (v1.23.0) - Removing symfony/polyfill-intl-icu (v1.23.0) - Removing symfony/polyfill-intl-grapheme (v1.23.0) - Removing symfony/polyfill-iconv (v1.23.0) - Removing symfony/polyfill-ctype (v1.23.0) - Removing symfony/options-resolver (v4.4.25) - Removing symfony/monolog-bundle (v3.5.0) - Removing symfony/monolog-bridge (v4.4.26) - Removing symfony/mime (v5.3.2) - Removing symfony/lock (v5.3.2) - Removing symfony/intl (v4.4.25) - Removing symfony/inflector (v5.3.0) - Removing symfony/http-kernel (v4.4.26) - Removing symfony/http-foundation (v4.4.26) - Removing symfony/http-client-contracts (v2.4.0) - Removing symfony/http-client (v4.4.26) - Removing symfony/framework-bundle (v4.4.26) - Removing symfony/form (v4.4.26) - Removing symfony/flex (v1.13.3) - Removing symfony/finder (v4.4.25) - Removing symfony/filesystem (v4.4.26) - Removing symfony/expression-language (v4.4.25) - Removing symfony/event-dispatcher-contracts (v1.1.9) - Removing symfony/event-dispatcher (v4.4.30) - Removing symfony/error-handler (v4.4.26) - Removing symfony/dotenv (v4.4.25) - Removing symfony/doctrine-bridge (v4.4.25) - Removing symfony/deprecation-contracts (v2.4.0) - Removing symfony/dependency-injection (v4.4.26) - Removing symfony/debug (v4.4.25) - Removing symfony/css-selector (v4.4.25) - Removing symfony/console (v4.4.26) - Removing symfony/config (v4.4.26) - Removing symfony/cache-contracts (v2.4.0) - Removing symfony/cache (v4.4.26) - Removing symfony/asset (v4.4.25) - Removing swiftmailer/swiftmailer (v6.2.7) - Removing studio-42/elfinder (2.1.59) - Removing stack/run (v1.1.0) - Removing stack/builder (v1.0.6) - Removing sparkpost/sparkpost (2.3.0) - Removing simshaun/recurr (v3.1.1) - Removing sensio/framework-extra-bundle (v6.1.5) - Removing sendgrid/sendgrid (6.2.0) - Removing sendgrid/php-http-client (3.14.0) - Removing robrichards/xmlseclibs (3.1.1) - Removing ramsey/uuid (3.9.3) - Removing ralouphie/getallheaders (3.0.3) - Removing psy/psysh (v0.10.8) - Removing psr/simple-cache (1.0.1) - Removing psr/http-message (1.0.1) - Removing psr/http-factory (1.0.1) - Removing psr/http-client (1.0.1) - Removing psr/container (1.1.1) - Removing psr/cache (1.0.1) - Removing predis/predis (v1.1.7) - Removing phpstan/phpdoc-parser (0.5.5) - Removing phpseclib/phpseclib (3.0.9) - Removing phpoffice/phpspreadsheet (1.18.0) - Removing php-http/promise (1.1.0) - Removing php-http/message-factory (v1.0.2) - Removing php-http/message (1.11.1) - Removing php-http/httplug (2.2.0) - Removing php-http/guzzle7-adapter (1.0.0) - Removing php-http/discovery (1.14.0) - Removing php-amqplib/rabbitmq-bundle (2.7.1) - Removing php-amqplib/php-amqplib (v3.0.0) - Removing pda/pheanstalk (v4.0.3) - Removing paragonie/random\_compat (v2.0.20) - Removing paragonie/constant\_time\_encoding (v2.4.0) - Removing oneup/uploader-bundle (3.1.2) - Removing noxlogic/ratelimit-bundle (1.17.0) - Removing nikic/php-parser (v4.11.0) - Removing myclabs/php-enum (1.8.3) - Removing mustangostang/spyc (0.6.3) - Removing mtdowling/jmespath.php (2.6.1) - Removing mrclay/minify (2.2.0) - Removing monolog/monolog (1.26.1) - Removing misd/phone-number-bundle (v1.3.2) - Removing maxmind/web-service-common (v0.8.1) - Removing maxmind-db/reader (v1.10.1) - Removing mautic/core-lib (3.2.x-dev), source is still present in app Deleting app/ - not deleted - Removing matomo/device-detector (4.3.0) - Removing markbaker/matrix (2.1.3) - Removing markbaker/complex (2.0.3) - Removing malkusch/lock (v1.4) - Removing maennchen/zipstream-php (2.1.0) - Removing lightsaml/symfony-bridge (1.3.0) - Removing lightsaml/sp-bundle (1.2.1) - Removing lightsaml/lightsaml (1.4.1) - Removing leezy/pheanstalk-bundle (4.0.1) - Removing league/mime-type-detection (1.7.0) - Removing league/flysystem-cached-adapter (1.1.0) - Removing league/flysystem (1.1.4) - Removing laminas/laminas-code (4.4.2) - Removing knplabs/knp-menu-bundle (v3.1.0) - Removing knplabs/knp-menu (v3.2.0) - Removing knplabs/gaufrette (v0.9.0) - Removing kamermans/guzzle-oauth2-subscriber (v1.0.10) - Removing joomla/string (1.4.5) - Removing joomla/filter (1.3.5) - Removing jms/serializer-bundle (3.9.1) - Removing jms/serializer (3.13.0) - Removing jms/metadata (2.5.0) - Removing jbroadway/urlify (1.2.2-stable) - Removing ip2location/ip2location-php (7.2.5) - Removing intervention/image (2.6.0) - Removing helios-ag/fm-elfinder-bundle (10.1) - Removing guzzlehttp/psr7 (1.8.2) - Removing guzzlehttp/promises (1.4.1) - Removing guzzlehttp/oauth-subscriber (0.5.0) - Removing guzzlehttp/guzzle (7.3.0) - Removing giggsey/locale (1.9) - Removing giggsey/libphonenumber-for-php (8.12.28) - Removing geoip2/geoip2 (v2.11.0) - Removing gaufrette/extras (v0.1.0) - Removing gaufrette/aws-s3-adapter (v0.4.0) - Removing friendsofsymfony/rest-bundle (3.0.5) - Removing friendsofsymfony/oauth2-php (1.3.1) - Removing friendsofsymfony/oauth-server-bundle (dev-doctrine-fix 605d207) - Removing friendsofphp/proxy-manager-lts (v1.0.5) - Removing ezyang/htmlpurifier (v4.13.0) - Removing egulias/email-validator (3.1.1) - Removing doctrine/sql-formatter (1.1.1) - Removing doctrine/persistence (2.2.1) - Removing doctrine/orm (2.9.3) - Removing doctrine/migrations (2.3.4) - Removing doctrine/lexer (1.2.1) - Removing doctrine/instantiator (1.4.0) - Removing doctrine/inflector (2.0.3) - Removing doctrine/event-manager (1.1.1) - Removing doctrine/doctrine-migrations-bundle (2.2.2) - Removing doctrine/doctrine-fixtures-bundle (3.4.0) - Removing doctrine/doctrine-bundle (2.4.2) - Removing doctrine/deprecations (v0.5.3) - Removing doctrine/dbal (2.13.2) - Removing doctrine/data-fixtures (1.4.4) - Removing doctrine/common (3.1.2) - Removing doctrine/collections (1.6.7) - Removing doctrine/cache (2.1.1) - Removing doctrine/annotations (1.13.1) - Removing composer/package-versions-deprecated (1.11.99.1) - Removing composer/installers (v1.11.0) - Removing composer/ca-bundle (1.2.10) - Removing clue/stream-filter (v1.5.0) - Removing barryvdh/elfinder-flysystem-driver (v0.2.1) - Removing bandwidth-throttle/token-bucket (2.0.0) - Removing aws/aws-sdk-php (3.185.17) - Installing mautic/api-library (3.0.0): Extracting archive Generating autoload files ---
**Author:** ![nickbm](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/nickbm/32/6488_2.png) [@nickbm](https://forum.mautic.org/u/nickbm)\ **Post date:** [December 18, 2021, 8:31pm UTC](https://forum.mautic.org/t/fatal-error-since-installed-mautic-api/22071/3 "2021-12-18T20:31:25Z")
My entire Mautic installation broke ☹ ---
**Author:** ![siljo](https://avatars.discourse-cdn.com/v4/letter/s/7ea924/32.png) [@siljo](https://forum.mautic.org/u/siljo)\ **Post date:** [March 18, 2024, 3:51am UTC](https://forum.mautic.org/t/fatal-error-since-installed-mautic-api/22071/4 "2024-03-18T03:51:37Z")
Hi, I’m facing a similar issue and looking for a solution, did you resolve your issue?