MyBB Community Forums

On my forum guests can post but after yesterday if guest post it will show this message 

MyBB has experienced an internal SQL error and cannot continue.
SQL Error:2006 - MySQL server has gone awayQuery:SELECT lastpost,fid FROM mybb_threads WHERE lastposteruid='0' AND tid='99' LIMIT 1
Please contact the MyBB Group for technical support.

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I have temporarily disable guest posting till I can fix this

Quote:SQL Error:2006 - MySQL server has gone away

have you recently added any plugin related to guests posting ?
if not then the issue is not related to MyBB and you need to contact your web host for fixing.