I was doing some subscriber dungeon levels and noticed that I wasn’t subscribed anymore so I was confused because I was doing and completing subscriber levels without needing to subscribe in dungeon. It also worked for forest and desert but for some reason not mountain.
Trick question. 
lol
It’s probably because you had already started the subscriber levels.
If you opened level once, than you can open it any time since this moment.
But also there are some bugs on server 
okay
(20 characters)