No data received after server migration

I am in the midst of transferring my data from one server to another (with a new IP). I have created all the databases on the new server, but I had to change the database username on the new server. I made these changes in db-config.php and wp-config.php.

Now the site will not load. I noticed if I alter creds in the config files that the site will render a "Error establishing a database connection", so I know it's talking to the MySQL server, but I don't know why my sites aren't working.

FWIW, other .php type sites are working on this server, so it appears that the right PHP handler is in place and working.

Can you make any suggestions?