We're Webflow experts here, but we recently came across the following error when migrating a client site to our hosting for them:-
Actually the fix turned out to be pretty simple. Open up the Joomla 'configuration.php' file and then change the following line:-
If you are still have database issues after this fix then check that you are using the correct database name, database username and password. Ensure that the user on the database is assigned to the database with all required privileges.