There's a massive bug with purchases for the last 5 updates now. You have to save after buying anything then load the saved data after you finish it. Some of the time it says you saved buy ends up loading info from before the buy / most recent save after it. Aka you buy something, use it, then on reload its gone and nothing it was used towards so you lose what was done with purchase and keeping it with both situations. Then the server data saves a higher wave clear so no credit till redone