# Fatal error: Uncaught Error: Interface 'JsonSerializable' **URL:** \ **Category:** Mautic 4 Install/Upgrade Support\ **Created:** [July 11, 2022, 1:34am UTC](https://forum.mautic.org/t/fatal-error-uncaught-error-interface-jsonserializable/24731 "2022-07-11T01:34:24Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![vscoder](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/vscoder/32/7918_2.png) [@vscoder](https://forum.mautic.org/u/vscoder)\ **Post date:** [July 11, 2022, 1:34am UTC](https://forum.mautic.org/t/fatal-error-uncaught-error-interface-jsonserializable/24731/1 "2022-07-11T01:34:24Z")
**Your software** _My PHP version is_ :7.4.30 _My MySQL/MariaDB version is_ 10.3.34-MariaDB-0ubuntu0.20.04.1 **Updating/Installing Errors** _I am_ (delete as applicable): Installing _Upgrading/installing via_ (delete as applicable) :Command Line _These errors are showing in the Mautic log_ : Fatal error: Uncaught Error: Interface ‘JsonSerializable’ not found in /web/vendor/sendgrid/sendgrid/lib/helpers/mail/Mail.php:15 Stack trace: #0 /web/vendor/composer/autoload\_real.php(55): require() #1 /web/vendor/composer/autoload\_real.php(38): composerRequirefcf81358727006a9595bdc8216684a1c(‘9dda55337a76a24…’, ‘/web/vendor/com…’) #2 /web/vendor/autoload.php(12): ComposerAutoloaderInitfcf81358727006a9595bdc8216684a1c::getLoader() #3 /web/autoload.php(3): require(‘/web/vendor/aut…’) #4 /web/bin/console(21): require\_once(‘/web/autoload.p…’) #5 {main} thrown in /web/vendor/sendgrid/sendgrid/lib/helpers/mail/Mail.php on line 15 **Your problem** _My problem is_ : This is a cron job failing. I assume for mailing I have one mail job in the que and it is not succeeding. ---
**Author:** ![silavapi](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/silavapi/32/7424_2.png) [@silavapi](https://forum.mautic.org/u/silavapi)\ **Post date:** [July 11, 2022, 8:39am UTC](https://forum.mautic.org/t/fatal-error-uncaught-error-interface-jsonserializable/24731/2 "2022-07-11T08:39:55Z")
Also reported in GitHub > > > \### Mautic Version > > 4.3.x series > > \### PHP version > > 7.4.30 > > \### What browsers are… you seeing the problem on? > > Not relevant > > \### What happened? > > A bug happened! I am getting this error in my system log : > Fatal error: Uncaught Error: Interface 'JsonSerializable' not found in /web/vendor/sendgrid/sendgrid/lib/helpers/mail/Mail.php:15 > Stack trace: > \#0 /web/vendor/composer/autoload\_real.php(55): require() > \#1 /web/vendor/composer/autoload\_real.php(38): composerRequirefcf81358727006a9595bdc8216684a1c('9dda55337a76a24...', '/web/vendor/com...') > \#2 /web/vendor/autoload.php(12): ComposerAutoloaderInitfcf81358727006a9595bdc8216684a1c::getLoader() > \#3 /web/autoload.php(3): require('/web/vendor/aut...') > \#4 /web/bin/console(21): require\_once('/web/autoload.p...') > \#5 {main} > thrown in /web/vendor/sendgrid/sendgrid/lib/helpers/mail/Mail.php on line 15 > > \### How can we reproduce this issue? > > Step 1: This is a standard install on a stand alone vps with no other software co existing with it. > > \### Relevant log output > > \`\`\`shell > Fatal error: Uncaught Error: Interface 'JsonSerializable' not found in /web/vendor/sendgrid/sendgrid/lib/helpers/mail/Mail.php:15 > Stack trace: > \#0 /web/vendor/composer/autoload\_real.php(55): require() > \#1 /web/vendor/composer/autoload\_real.php(38): composerRequirefcf81358727006a9595bdc8216684a1c('9dda55337a76a24...', '/web/vendor/com...') > \#2 /web/vendor/autoload.php(12): ComposerAutoloaderInitfcf81358727006a9595bdc8216684a1c::getLoader() > \#3 /web/autoload.php(3): require('/web/vendor/aut...') > \#4 /web/bin/console(21): require\_once('/web/autoload.p...') > \#5 {main} > thrown in /web/vendor/sendgrid/sendgrid/lib/helpers/mail/Mail.php on line 15 > \`\`\` > > > \### Code of Conduct > > \- \[X\] I confirm that I have read and agree to follow this project's Code of Conduct Connecting up for visibility. ---
**Author:** ![silavapi](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/silavapi/32/7424_2.png) [@silavapi](https://forum.mautic.org/u/silavapi)\ **Post date:** [July 11, 2022, 8:41am UTC](https://forum.mautic.org/t/fatal-error-uncaught-error-interface-jsonserializable/24731/3 "2022-07-11T08:41:45Z")
Can you double check the PHP version in the system information page for Mautic, just to be sure the correct PHP version is being loaded (sometimes you can get CLI using a different version to the application). ---
**Author:** ![vscoder](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/vscoder/32/7918_2.png) [@vscoder](https://forum.mautic.org/u/vscoder)\ **Post date:** [July 11, 2022, 10:08am UTC](https://forum.mautic.org/t/fatal-error-uncaught-error-interface-jsonserializable/24731/4 "2022-07-11T10:08:28Z")
Hello, Yes from the system info of mautic it reports PHP Version 7.4.30. From the cli: # php -v PHP 7.4.30 (cli) (built: Jun 10 2022 13:33:17) ( NTS ) Copyright (c) The PHP Group Zend Engine v3.4.0, Copyright (c) Zend Technologies with Zend OPcache v7.4.30, Copyright (c), by Zend Technologies Thanks for looking into this with me! Brad ---
**Author:** ![silavapi](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/silavapi/32/7424_2.png) [@silavapi](https://forum.mautic.org/u/silavapi)\ **Post date:** [July 11, 2022, 10:12am UTC](https://forum.mautic.org/t/fatal-error-uncaught-error-interface-jsonserializable/24731/5 "2022-07-11T10:12:41Z")
OK and which version of Mautic are you using, as that was omitted in your original post. ---
**Author:** ![vscoder](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.mautic.org/vscoder/32/7918_2.png) [@vscoder](https://forum.mautic.org/u/vscoder)\ **Post date:** [July 11, 2022, 10:26am UTC](https://forum.mautic.org/t/fatal-error-uncaught-error-interface-jsonserializable/24731/6 "2022-07-11T10:26:32Z")
> [@silavapi](#): > > [Fatal Error with sendgrid · Issue #11326 · mautic/mautic · GitHub](https://github.com/mautic/mautic/issues/11326) I am using: Copyright 2022 Mautic. All Rights Reserved. v4.3.1