Upgraded to 2.16, and now it won't work on any contact uploads

Your software
My Mautic version is:2.16
My PHP version is:7.0

Your problem
My problem is:
Can’t load contacts
These errors are showing in the log:
[2020-07-21 09:20:45] mautic.CRITICAL: Uncaught PHP Exception Doctrine\DBAL\Exception\DriverException: “An exception occurred while executing ‘SELECT m0_.is_published AS is_published_0, m0_.date_added AS date_added_1, m0_.created_by AS created_by_2, m0_.created_by_user AS created_by_user_3, m0_.date_modified AS date_modified_4, m0_.modified_by AS modified_by_5, m0_.modified_by_user AS modified_by_user_6, m0_.checked_out AS checked_out_7, m0_.checked_out_by AS checked_out_by_8, m0_.checked_out_by_user AS checked_out_by_user_9, m0_.id AS id_10, m0_.username AS username_11, m0_.password AS password_12, m0_.first_name AS first_name_13, m0_.last_name AS last_name_14, m0_.email AS email_15, m0_.position AS position_16, m0_.timezone AS timezone_17, m0_.locale AS locale_18, m0_.last_login AS last_login_19, m0_.last_active AS last_active_20, m0_.online_status AS online_status_21, m0_.preferences AS preferences_22, m0_.signature AS signature_23, m1_.is_published AS is_published_24, m1_.date_added AS date_added_25, m1_.created_by AS created_by_26, m1_.created_by_user AS created_by_user_27, m1_.date_modified AS date_modified_28, m1_.modified_by AS modified_by_29, m1_.modified_by_user AS modified_by_user_30, m1_.checked_out AS checked_out_31, m1_.checked_out_by AS checked_out_by_32, m1_.checked_out_by_user AS checked_out_by_user_33, m1_.id AS id_34, m1_.name AS name_35, m1_.description AS description_36, m1_.is_admin AS is_admin_37, m1_.readable_permissions AS readable_permissions_38, m0_.role_id AS role_id_39 FROM ma_users m0_ LEFT JOIN ma_roles m1_ ON m0_.role_id = m1_.id WHERE (m0_.username = ? OR m0_.email = ?) AND m0_.is_published = ?’ with params [“bkroeger”, “bkroeger”, 1]: SQLSTATE[HY000]: General error: 2006 MySQL server has gone away” at /home/v7x72z6sq727/public_html/vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/AbstractMySQLDriver.php line 115 {“exception”:"[object] (Doctrine\DBAL\Exception\DriverException(code: 0): An exception occurred while executing ‘SELECT m0_.is_published AS is_published_0, m0_.date_added AS date_added_1, m0_.created_by AS created_by_2, m0_.created_by_user AS created_by_user_3, m0_.date_modified AS date_modified_4, m0_.modified_by AS modified_by_5, m0_.modified_by_user AS modified_by_user_6, m0_.checked_out AS checked_out_7, m0_.checked_out_by AS checked_out_by_8, m0_.checked_out_by_user AS checked_out_by_user_9, m0_.id AS id_10, m0_.username AS username_11, m0_.password AS password_12, m0_.first_name AS first_name_13, m0_.last_name AS last_name_14, m0_.email AS email_15, m0_.position AS position_16, m0_.timezone AS timezone_17, m0_.locale AS locale_18, m0_.last_login AS last_login_19, m0_.last_active AS last_active_20, m0_.online_status AS online_status_21, m0_.preferences AS preferences_22, m0_.signature AS signature_23, m1_.is_published AS is_published_24, m1_.date_added AS date_added_25, m1_.created_by AS created_by_26, m1_.created_by_user AS created_by_user_27, m1_.date_modified AS date_modified_28, m1_.modified_by AS modified_by_29, m1_.modified_by_user AS modified_by_user_30, m1_.checked_out AS checked_out_31, m1_.checked_out_by AS checked_out_by_32, m1_.checked_out_by_user AS checked_out_by_user_33, m1_.id AS id_34, m1_.name AS name_35, m1_.description AS description_36, m1_.is_admin AS is_admin_37, m1_.readable_permissions AS readable_permissions_38, m0_.role_id AS role_id_39 FROM ma_users m0_ LEFT JOIN ma_roles m1_ ON m0_.role_id = m1_.id WHERE (m0_.username = ? OR m0_.email = ?) AND m0_.is_published = ?’ with params [“bkroeger”, “bkroeger”, 1]:\n\nSQLSTATE[HY000]: General error: 2006 MySQL server has gone away at /home/v7x72z6sq727/public_html/vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/AbstractMySQLDriver.php:115, Doctrine\DBAL\Driver\PDOException(code: HY000): SQLSTATE[HY000]: General error: 2006 MySQL server has gone away at /home/v7x72z6sq727/public_html/vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/PDOStatement.php:107, PDOException(code: HY000): SQLSTATE[HY000]: General error: 2006 MySQL server has gone away at /home/v7x72z6sq727/public_html/vendor/doctrine/dbal/lib/Doctrine/DBAL/Driver/PDOStatement.php:105)"}
[2020-07-21 09:22:06] mautic.ERROR: PHP Error: Maximum execution time of 30 seconds exceeded - in file /home/v7x72z6sq727/public_html/vendor/doctrine/orm/lib/Doctrine/ORM/UnitOfWork.php - at line 725
[2020-07-21 09:22:06] mautic.ERROR: Symfony\Component\Debug\Exception\FatalErrorException: Error: Maximum execution time of 30 seconds exceeded - in file /home/v7x72z6sq727/public_html/vendor/doctrine/orm/lib/Doctrine/ORM/UnitOfWork.php - at line 725

Steps I have tried to fix the problem: I’ve monitored my resources and they’re not maxing out, I’ve increased the max upload time and increased memory limit to no avail.

Maximum execution time of 30 seems to be the issue here. If you’re managing the server you need to increase this. This has more to do with your WebServer setup than it with Mautic. The insertion of the data in the Database takes more than 30 Seconds in this case. The server only allows it to run for 30 Seconds before killing the action which leads to your error.