I have noticed that many users have problems with Jailkit's. First thing you should do is log in as the Reseller and Account User. Can you see Shell options there? If not you know that the problem is there. Log in as admin and check out the Reseller/Client options. Is the option "Max. number of Shell users" in use? If you have ISPconfig cluster what is the clients default server/node? More often than not these questions will lead you to the right answers you are seeking.
PS. After you changed the clients default server (if you have a cluster setup) and you have added Shell user's don't forget to change the Jailkit option to "None" and Save then after a 1min change it back to Jailkit. This way the settings should stick.
