I play via Steam and my in-game purchases have not worked for months. I just tried to use the Redeem Code for the IDLERFEST code redemption and all I get after clicking Confirm is a Failed to redeem code! message with a large red triangle and text telling me the Connection to rewards server timed out. Either you code was entered wrong or there was a problem with your internet connection.
Tthe code was right and there is nothing wrong with my internet connection. I'm assuming the same thing that prevents in-game purchases is causing this too.