The Treat Calendar haven't yet reached all players and their games since it's still running as a test feature.
The calendar may still have some issues or not working perfectly for all players. It may also disappear from the game some periods or on some devices.
We are monitoring the feature closely and hopefully it will work smoothly and also be introduced for all players in the future.
If you don't get the reward from the calendar or if it's stuck on the first day, don't worry, you'll still have the Daily Booster Wheel that gives you a treat every day until we've got the calendar on the right track.