Unable to log into ECP/OWA after fresh exchange 2013 install

Hello,

We recently installed Exchange 2013 in a new environment and realized we were unable to connect to ECP or OWA. We get the logon page, enter VALID credentials and the page refreshes and requests credentials again.

We verified:

The install account has an enabled mailbox

Typing in INVALID credentials will generate an INVALID credential error.

We can make changes via exchange management shell with the install account.

Any help would be greatly appreciated.

Thanks!
-dan