The issue for Facebook Canvas should be resolved now. Please make sure that if the loading screen still says 4.5 or 4.5.1 to clear the cache. Only on version 4.5.2 (for FB canvas users) it is not crashing.
Thank you again for your patience!
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Dear FB Canvas players,
We are working on fixing an issue which prevents players from accessing the game. We will keep you in the loop and apologize for the inconvenience.
Your Royal Revolt 2 team