You should be able to call registerHook with no active room. It sets the “hook” URL for the full account.
I think the roomInstance in this case is the “account” path so I don’t understand where it would fail.
Did you correctly created the AccountManager instance and logged in successfully ? What language are you developing in ?
The sequence should be something like:
am = AccountManager.new(“http://collaboration.adobelivecycle.com/”);
am.login(username, password);
am.registerHook(hookURL);