Access denied after migrating to new web host

[Xenodream]

I migrated to a new web host, using the same domain name. I created the database and user with the same names and password, identical to the config.php setttings. Forum is 1.8.33.
But I get 1045 - Access denied for user 'mybb_4'@'localhost' (using password: YES)
I tried changing the password for the user and config.php but it doesn't help.

What could the problem be?

[Xenodream]

My old host was running MySQL 5.1.73. The database config had database mybb_1
Host: localhost:3306 (MySQL) Users: [mybb_4]

The new host is running MariaDB 10.3.39
The database has fixed prefixes for the user, so the database is xenodrea_mybb_1
phpmyadmin shows localhost:3306 database xenodrea_mybb_1
and the user is xenodrea_mybb_4
but the prefixes are for hosting user id and not used locally. If I include them in either database or user in the config.php I just get "SQL error: 0- " so that doesn't seem to be the problem.

I followed the migration instructions exactly and everything went perfectly apart from the forum not being able to connect to the database.
Nobody has any ideas?

---

My mistake: I hadn't completed adding the user to the database with full permissions. After that, I did have to include the prefixes for the full database and user names in the config.db.

The migration instructions could have little more detail for those who haven't created databases and added users before.