I just recently changed host and I got this error shown below. I imported the database... created the new MySQL user and changed them in the inc/config.php file.
MyBB was unable to load the SQL extension.
Thanks!
Are you sure the DB is MySQL? Also has the user got full access to the database?
Please have a look at the common errors Wiki page:
[Wiki: Help:Common_Error_Messages] (Broken link, head over to docs.mybb.com instead)
If you have any other questions about this error, please feel free to reply, including any extra details if necessary such as the link to the error, plugins/modifications installed, and/or a test account.
With regards,
MyBB Support Team