I don't know what might be causing that problem. Normally, if there is a problem like this, it is the other way around - the shop can be seen but not the admin. Please make sure the code changes have been made to the shops application_top.php file. And check both configure files to make sure the STORE_SESSIONS setting is set the same. You might also want to check what php version is being used. This addon should work with 7.0 but I haven't tested it above that. Other than those, I can't think of what else it might be. It would require troubleshooting at that point.