OJS DB Error:MySQL server has gone away

Hi all,
I am using OJS, when today suddenly DB Error: MySQL server has gone away, every time I clicks the Journal Manager role (link). This never happen before. I already try to increase the connection time, change the citation_checking_max_processes to 10, persistent connection set to on, but nothing happen.

Help me please, I am doing publishing process right now. Thanks

you need to look in error logs. to provide more info