Please send your ordernumber from Google Play to us through the feedback system in Kryss.
Then we will fix the problem.
Please send a screenshot of your purchase history on your device.
Like this:

Use the feedback system in Kryss
This happens in the last turns of a game, after all letters are assign to the players.
The reason your are not getting any new, is because your opponent has all the remaining letters and was not able to place them all correctly.
After all letters are assigned to the players, each player has one turn left to complete the game. When this happens a message saying This is your last turn. If you do not place your letters correctly in this turn the game will end, even if you have letters left.