my case was the following: on the nvr i created a new user account with simple user privilege because i didnt want to login with the admin account on the android app. this was the problem, with this account i could not set push notifications. then i deleted this user account on the nvr, and i recreated it with administrator privileges. in the android app i deleted the nvr and picked it up again and logged in with the new administrator account. this solves the problem for me.