Log in to admin no longer works after host changed servers

My website lived on a shared server that my host provider decommissioned last week without realizing that a working site was still on the server. Zen v 1.3.9h has been working on that site for years. The host provider moved my site to a new server (with a new IP address), but since the move I have found that I can no longer use the admin side of my Zen Cart installation. The public portion appears to work correctly.

When I log into Zen Cart Admin, login is successful and the usual admin home page page is displayed. Any activity on that page (links or menu selections) sends me back to the log in screen. This suggests that authentication is working but something else is broken. Names servers and site certificate have been updated. I have cleared my browser cache, cookies and history but the problem persists.

I am at a loss as to where to look for the problem. The web host hasn't responded to a support ticket yet either.

Disable SSL. This is not necessarily a solution, but a way of eliminating one of the possible causes.

Cheers
Rod

Thank you for the response.

I discovered a few hours ago that the SSL certificate on my site is not installed the same as the previous one. I changed the www part of server urls in configure.php and part of this problem is solved (so you were correct!)

There are more problems, but at least his one if solved.

Thanks!

For those that encounter this problem, check file and folder permissions. These were not carried over from old site to the new site. The last one was really hard to find.