WP-Admin Login Panel Does Not Appear – Can't Login

Please help!

I had the domain in question as a subdomain on a hosting package with Hostgator, with WordPress installed, and working.

I have now taken a separate hosting package with Hostgator, and installed the domain (cowran.com) as the root domain. I installed WordPress, with a view to later installing multisite. At the time of installation on the new hosting package, I had not removed cowran.com from the subdomains on the other hosting package…

WordPress installed correctly, but when I go to cowran.com/wp-admin no login panel appears, and the domain shows an ad page…

Any help would be gratefully received!!