I have exactly the same questions as found in this post: https://compojoom.com/forum/post/how-to-edit-user-data-and-list-sync-broken.
I am using the Community Builder plugin with CMC and the registration works fine to subscribe a user.
The checkbox and "Subscribe" buttons appear on the user profile display page, but 1) it doesn't seem to be aware of whether the current Joomla user is subscribed or not, and 2) checking the check box and clicking "Subscribe" returns a message "404: The requested resource could not be found". (See screenshot)
I would like to know:
1. Is it possible to get the subscribe button working on either the User Profile or Edit User Profile CB pages?
2. Is it possible to enable this checkbox on the back end administration user profile edit interface, or does the user always have to be managed in the CMC component interface?