I upgraded my OJS from 3.1.2.1 to 3.2.0.2. to do this I had to upgrade my PHP from 7.1 to 7.3.
I encountered an error while publishing, the error in status: 405. “An unexpected error has occurred, You may have been logged out, please reload the page and try again.”
If you encounter this error, to fix it:
After long tests, I found out that the server was incomplete. I had to ask the server provider to finalize the upgrade of PHP, hint was to fix the whitelist in Apache.
Then I encountered another error status: 500 PUT.
Slim Application Error:
Type: Exception
Message: DB Error: Illegal mix of collations (utf8_unicode_ci,IMPLICIT) and (utf8_general_ci,IMPLICIT) for operation ‘=’ Query
To fix this you have to go to phpmyadmin and change Collation utf8_unicode_ci to utf8_general_ci
Ask the server provider about it, they will help you.
This was a long process, it took me a long time to fix.
I hope this helps other people.
I have the same error, but without the PHP upgrade