Can not switch from localhost to public IP

I installed Zen Cart 1.3.6. It works fine when I intalled it as localhost. My server has a public IP address. If I switch the localhost to public IP address, the index.php page flashes for a second and then I got the page not found error.

Here is what I did:

1. Install as localhost for the HTTP, HTTPS and MySQL database. Tested it.
2. Modify the configure.php to replace the "localhost" with the public IP for the following
   define('HTTP_SERVER', 'http:/localhost');
   define('HTTPS_SERVER', 'https://localhost');

I saw the first page flashes and then got the "page not found" error.
Then I tried to install the ZenCart using the public IP, I got the same error.

I suspect this has something to do the session. Because if I remove the php files that used the "$_SESSION" variables from the sandbox folder, I can see the page banner.

Please advise.

Thanks a lot,

Have you changed both the shop and admin configure.php files to reflect the new IP?

includes/configure.php

and

admin/includes/configure.php

Yes, I did.