My forum is showing  Error code: EX1142  
Also: 

Fatal error: Uncaught exception 'IPS\Db\Exception' with message 'INSERT,DELETE command denied to user 'mywebsite'@'localhost' for table 'core_sessions'' in /var/www/mywebsite/html/forum/system/Db/Db.php:386 Stack trace: #0 /var/www/mywebsite/html/forum/system/Db/Db.php(668): IPS\_Db->preparedQuery('REPLACE INTO `c...', Array) #1 /var/www/mywebsite/html/forum/system/Session/Front.php(298): IPS\_Db->replace('core_sessions', Array, true) #2 [internal function]: IPS\Session\_Front->write('eb10be5281a6b33...', '') #3 [internal function]: session_write_close() #4 {main} thrown in /var/www/mywebsite/html/forum/system/Db/Db.php on line 386

Any help on this?

1 hour ago, Martin Bazuin said:

My forum is showing  Error code: EX1142  
Also: 

Fatal error: Uncaught exception 'IPS\Db\Exception' with message 'INSERT,DELETE command denied to user 'mywebsite'@'localhost' for table 'core_sessions'' 

Have you checked the permissions of your Database/MySQL-user?  (Insert / delete)

Do you have enough space left in for the databases?

As TheSonic noted, that error points to the Database User not having the correct permissions. "INSERT,DELETE command denied to user"

The user must have full permissions. I'd suggest contacting your Host and asking them to fix that.