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. 

You may want to contact Obsidian directly at https://support.obsidian.net/article/12-looking-for-help-on-our-older-games# and scroll down to "contact us". This forum is primarily for peer-to-peer support at this point.