Typically, database errors of this kind are caused by the information being incorrect in the config file for the website or there is an issue with the database servers themselves. Double check all the DB login information for your site. If that's not the cause, then calling into support will probably be your best bet.
Once your issue is resolved,
please be sure to come back and click accept for the solution
Unfortunately, the DB login data are all correct. I tried to call the support 3 times. After 15 minutes waiting the call stop by itself....