Thank you very much for helping me. I Will look into it and mail my client to tell her to do the above.
[29-Jul-2022 13:01:27 UTC] PHP Fatal error: Classes\Mail_Integration_365\Mail::send(): The script tried to execute a method or access a property of an incomplete object. Please ensure that the class definition "TheNetworg\OAuth2\Client\Token\AccessToken" of the object you are trying to operate on was loaded _before_ unserialize() gets called or provide an autoloader to load the class definition in /home/dickyuh308/domains/organisatielotus.nl/public_html/wp-content/plugins/mail-integration-365/classes/mail_integration_365/mail.php on line 151
So I deactivated the Mail integration plugin and no error anymore in UM. So strange.
What can I do with the other plugin?
