I think the latest update might have broken completing challenges. I completed my challenge earlier today (5/5 Allies Acquired - A Friend Indeed). It shows completed, and has the checkbox checked. The Happy Holidays tracker now shows 1/4. However the "Pickup Rewards" section for the Challenges does not contain anything for me to pick-up. Sad day.
Just wanted to mention it in case this is a new issue and others encounter the same problem.
I'm on the phone version of the game if that helps.