Database Connection Error

Hello!

So I took a completely functioning site that is up and copied everything over to another server.

I want this site to connect to the same database so I did not change anything in wp-config

I am getting the error: ‘Error establishing a database connection’
from a wordpress looking page when accessing the site on the new server

The Db has not changed and still works for the old site but will not for the new. Any explanation for this issue?

thank you