DBI connect failed after switching SQL server

hello

After changing mysql server ( localhost to SQL dedicated server ), I always have in virtualmin the same type of error message :

“DBI connect failed : Access denied for user ‘myuser’@’%’ to database ‘mysql’”

Curiously, I have completely access to the transferred tables when I click “Edit Databases”.
This section works perfectly.

Is “mysql” table that we have not transferred is critical to the operation of virtualmin ?
I do not think it was.
How in this case because the SQL dedicated server must already have a mysql table with its own information in.

Thank you for your indication !

B.