There is a problem with the Notification Options that are in the UCP if you try and use them in the ACP - or any other situation where you want to edit them for another user.

The basic problem is that in the get_subscription_types() function there is this line if ($type instanceof \phpbb\notification\type\type_interface && $type->is_available()) and it is the last part ($type->is_available())that is creating the issue. This calls the is_available() function in each of the notification types files and is using $this->user->data['user_id'] (or similar) - effectively using the current user which, if being accessed from the ACP, will be an Admin.

This area needs to utilise the sending of any user id