Title sort of says it all, I didn't change anything about the app lately. When I toggle "deactivate maintenance mode" it activates it again right-away without any explanation.
I think this is related due to maintaince work we did yesterday on IHP Cloud. The server was overloaded and as a quick fix I've stopped some apps taking lots of memory (only stopped apps that haven't been deployed for a while).
Can you run a new deployment? Then the app should be back.
The performance issues we've had yesterday have also been resolved. In general all new deployed apps use way less memory than "older" generation apps (deployed last month).