Board Thread:Questions and Answers/@comment-26757897-20150719175949/@comment-25090105-20150719182454

Most likely because the app detected a time fast-forward from the last time you access it.

Example: Assume now is 07:00. You change the time to 09:00, then open the app. You change the time back to 07:00, then open the app again.

The app remembers that the last access time was 09:00, but now it's actually 07:00, which is not possible unless the time is changed manually. Therefore, the app locks itself until the time is right (09:00 in this case). It serves to prevent time-cheating, I suppose.