It happened to me. You have to just wait a few minuets, or play a deck, remix it, and save. Worked for me.

I don't really know how to help but.. I'll try. Have you tried restarting your gadget? Or have you tried to delete castle and install it back? Or maybe refreshing castle and checking your wifi idk?? I'm sorry if none of this helps, I haven't experienced this before.

Ok guys.....i was making a super cool deck on my main account (huggy_wuggy8) i tried to save my deck but, nothing happened it refused to save the game, i tried, tried, and tried still the same thing, but in this account it worked ! I tried to update castle but still the same thing....please if this happened for you too, please help me gimme some solutions if u have, thanks for reading