Can't access admin area - stuck on login screen

After spending countless hours trying to figure out how to solve the issue, I would like to ask the pro's! I am an Open Cart newbie, and have recently taken over managing an Open Cart 1.5.6.4 site. We just moved the site from one dedicated hosting server to another (with the same hosting service). I used Filezilla to FTP the files to the new CPanel directory, and exported the DB from the prior host, and imported the tables into our new CPanel myPHP DB. After updating the config files to reflect the new DB, username, & password, the site comes up fine. When I attempted to access the admin page, it prompted me with the mysql depreciation error. I then updated the config files to use mysqli. The site and admin page load fine, but now I can't login to the admin page. It is recognizing the users, as it gives me an incorrect password error when I test it with an incorrect password. After reading nearly a hundred help forum pages, the nearest thing I can tell is that it must be some kind of sessions/cookie error? Like I said, the admin page loads just fine. But it won't allow me to login as ANY user, admin or others. It gives no errors, no nothing. Just refreshes back to the login screen. Any ideas? Help!!

Did you ever figure this out? I've got a similar issue.

make sure that the config files also reflect proper file path related to new server.
If still not possible to log in into admin there might be a database problem, and it should be solved on a database level.