I can’t watch video for time short or get free gems from a video for last 2 months, why?? 

Because sometimes around beginning of last December, their advertisement partner Vungle had ad campaigns in the loop that broke the local state on your system beyond repair.

If you’re playing on a Windows system, go to the folder %LOCALAPPDATA%\Packages\flaregamesGmbH.RoyalRevolt2_g0q0z3kw54rap\LocalState   (just paste this string into the address bar of a file explorer), and delete the folder  VungleSDK. Then wait a moment, restart the game, and videos should work again.

Hope this helps.