I installed Family Protection through my Time Warner Cable about 6 moths ago and everything was fine. I have recently tried to add a new user for my daughter and it says "You dont have permission to add new user". I have been able to delete and change all of the other four users that I setup so I don't understand what the problem is. I've tried logging off and on, restarting the computer and everything else I can think of with no luck.
Normally I would suggest that you contact McAfee Technical support. However since you obtained your subscription through your ISP. I recommend that you go to your account with Time Warner\Spectrum and either use 'Online Chat' for assistance, or call your local branch.My Account Login | Time Warner Cable
Just in case you still want to give McAfee Technical Support a call also: https://service.mcafee.com/webcenter/portal/cp/home/contact