I’ve worked for a couple of hosting companies. Here’s the fix.
1) go to your wp-config file for that site , and find the name of the database
2) go to cpanel and go to mySQL Databases
3) create a new user. When you create the user make sure you copy the password as you will need it later.
4) add the user to the database , typically I give all permissions
5) go back to the wp-config file. Find the password in it, replace the old password with the new password and replace the old user with the new user.
6) save the wp-config file
7) check your site.
If that does not resolve the database issue then there is a chance that there could be an issue with the hosting, such as MySQL not running on the server.
~Support Monkey
