I've been playing the old version for a while. I tried to update the game a lot of times but it just said something along the lines "Update Failed". After that i deleted the game and tried downloading it game but now it just says "app not installed" even though i have install unknown apps allowed...

Hm, might be an Android problem :/

The engine that I use sometimes doesn't play well with Android. I think there's nothing I can do here :(