/mautic/s/emails wont open

Your software
My Mautic version is: v2.16.0
My PHP version is: 7.3 (I think)
Installed on WHM / CPanel / CentoOS

Your problem
/mautic/s/emails wont open and I also cannot upgrade the database via http://[your-mautic-url]/s/update/schema, even though this is a brand new install.

The only thing I added was a zapier link to import emails from our wix.com website.

Steps I have tried to fix the problem:
I tried to clear the cache and update the database from the troubleshooting steps, neither seemed to work…

These errors are showing in the log:

[2020-05-14 15:34:47] mautic.NOTICE: Doctrine\DBAL\Exception\DriverException: An exception occurred while executing 'ALTER TABLE maux5_lead_event_log DROP FOREIGN KEY FK_2606AA855458D':  Can't DROP FOREIGN KEY `FK_2606AA855458D`; check that it exists (uncaught exception) at /home/deltaserver/public_html/mautic/vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/AbstractMySQLDriver.php line 115 while running console command `doctrine:migrations:migrate` [] []
[2020-05-14 15:34:47] mautic.ERROR: [UPGRADE ERROR] Exit code 1; Mautic Migrations \ Migrating up to 20190715065013 from 20180220212444 \ ++ migrating 20180329185634 \ -> ALTER TABLE maux5_lead_event_log DROP FOREIGN KEY FK_2606AA855458D Migration 20180329185634 failed during Execution. Error An exception occurred while executing 'ALTER TABLE maux5_lead_event_log DROP FOREIGN KEY FK_2606AA855458D': \ Can't DROP FOREIGN KEY `FK_2606AA855458D`; check that it exists \ [Doctrine\DBAL\Exception\DriverException] An exception occurred while executing 'ALTER TABLE maux5_lead_event_log DROP FOREIGN KEY FK_2606AA855458D': \ Can't DROP FOREIGN KEY `FK_2606AA855458D`; check that it exists \ [Doctrine\DBAL\Driver\Mysqli\MysqliException] Can't DROP FOREIGN KEY `FK_2606AA855458D`; check that it exists \ doctrine:migrations:migrate [--write-sql] [--dry-run] [--query-time] [--allow-no-migration] [--configuration [CONFIGURATION]] [--db-configuration [DB-CONFIGURATION]] [--db DB] [--em EM] [--shard SHARD] [-h|--help] [-q|--quiet] [-v|vv|vvv|--verbose] [-V|--version] [--ansi] [--no-ansi] [-n|--no-interaction] [-s|--shell] [--process-isolation] [-e|--env ENV] [--no-debug] [--] <command> [<version>] \ [] []
[2020-05-14 15:34:53] mautic.WARNING: PHP Warning - require(/home/deltaserver/public_html/mautic/app/cache/prod/doctrine/orm/Proxies/__CG__MauticCategoryBundleEntityCategory.php): failed to open stream: No such file or directory - in file /home/deltaserver/public_html/mautic/vendor/doctrine/common/lib/Doctrine/Common/Proxy/AbstractProxyFactory.php - at line 209 {"className":"Mautic\\CategoryBundle\\Entity\\Category","classMetadata":"[object] (Doctrine\\ORM\\Mapping\\ClassMetadata: Doctrine\\ORM\\Mapping\\ClassMetadataInfo@000000001b08be350000000069f70acd)","proxyClassName":"Proxies\\__CG__\\Mautic\\CategoryBundle\\Entity\\Category","fileName":"/home/deltaserver/public_html/mautic/app/cache/prod/doctrine/orm/Proxies/__CG__MauticCategoryBundleEntityCategory.php"} []
[2020-05-14 15:34:53] mautic.WARNING: PHP Warning - require(/home/deltaserver/public_html/mautic/app/cache/prod/doctrine/orm/Proxies/__CG__MauticCategoryBundleEntityCategory.php): failed to open stream: No such file or directory - in file /home/deltaserver/public_html/mautic/vendor/doctrine/common/lib/Doctrine/Common/Proxy/AbstractProxyFactory.php - at line 209 {"className":"Mautic\\CategoryBundle\\Entity\\Category","classMetadata":"[object] (Doctrine\\ORM\\Mapping\\ClassMetadata: Doctrine\\ORM\\Mapping\\ClassMetadataInfo@000000001b08be350000000069f70acd)","proxyClassName":"Proxies\\__CG__\\Mautic\\CategoryBundle\\Entity\\Category","fileName":"/home/deltaserver/public_html/mautic/app/cache/prod/doctrine/orm/Proxies/__CG__MauticCategoryBundleEntityCategory.php"} []
[2020-05-14 15:34:53] mautic.ERROR: PHP Notice: require(): Failed opening required '/home/deltaserver/public_html/mautic/app/cache/prod/doctrine/orm/Proxies/__CG__MauticCategoryBundleEntityCategory.php' (include_path='.:/opt/cpanel/ea-php72/root/usr/share/pear') - in file /home/deltaserver/public_html/mautic/vendor/doctrine/common/lib/Doctrine/Common/Proxy/AbstractProxyFactory.php - at line 209 [] []
[2020-05-14 15:34:53] mautic.ERROR: Symfony\Component\Debug\Exception\FatalErrorException: Notice: require(): Failed opening required '/home/deltaserver/public_html/mautic/app/cache/prod/doctrine/orm/Proxies/__CG__MauticCategoryBundleEntityCategory.php' (include_path='.:/opt/cpanel/ea-php72/root/usr/share/pear') - in file /home/deltaserver/public_html/mautic/vendor/doctrine/common/lib/Doctrine/Common/Proxy/AbstractProxyFactory.php - at line 209 [] []
[2020-05-14 15:34:53] mautic.CRITICAL: Uncaught PHP Exception Symfony\Component\Debug\Exception\FatalErrorException: "Compile Error: require(): Failed opening required '/home/deltaserver/public_html/mautic/app/cache/prod/doctrine/orm/Proxies/__CG__MauticCategoryBundleEntityCategory.php' (include_path='.:/opt/cpanel/ea-php72/root/usr/share/pear')" at /home/deltaserver/public_html/mautic/vendor/doctrine/common/lib/Doctrine/Common/Proxy/AbstractProxyFactory.php line 209 {"exception":"[object] (Symfony\\Component\\Debug\\Exception\\FatalErrorException(code: 0): Compile Error: require(): Failed opening required '/home/deltaserver/public_html/mautic/app/cache/prod/doctrine/orm/Proxies/__CG__MauticCategoryBundleEntityCategory.php' (include_path='.:/opt/cpanel/ea-php72/root/usr/share/pear') at /home/deltaserver/public_html/mautic/vendor/doctrine/common/lib/Doctrine/Common/Proxy/AbstractProxyFactory.php:209)"} []

Hello how are you?

Try to check your Mautic’s schema using ssh.

This link here can help you with some questions.
https://johnlinhart.com/blog/uh-oh-mautic-upgrade-was-not-successful