Today I bought a 3 chests for 500 coins. I opened two of them fine and saw the cards added to my stash. The third one I tried to open would show the beginning to open animation then immediately directed me back to the buy a chest screen. I tried this a couple of times. Then I restarted the game to see if that would fix things and my chest was gone. I checked my unclaimed stash to see if any new cards had been added with that third chest and it did not seem like there was anything new there.