Hi Puffin_time,
We appreciate you reaching out to us.
We'd like to gather additional details that may help us be in a better position to assist you.
What is the exact number of Move streak days to earn the award?
Are you still able to complete the challenge with the remaining days of December?
In the meantime, please check for a software update and make sure that you are running the latest version of iOS and watchOS.
While it isn't inherently assured that an update will resolve the issue, updating to the latest software version for your devices can help isolate potential software issues.
Kindly secure a backup and update.
How to back up your iPhone, iPad, and iPod touch
Update your iPhone, iPad, or iPod touch
Update your Apple Watch
Take care!