Hello and welcome to the forums,
The most likely reason for this error is problem with sql user permissions. If you've granted permissions manually for each action to the user designated to work for EPESI, it's possible you skipped the LOCK TABLES permission, resulting in the error you linked. To solve this issue, simply grant LOCK TABLES permission to the user on the selected database.
Please let us know if this was the problem.
Kind regards,
Arek
