I suggest performing a forced restart. Steps needed are found in the Apple Support article: Restart your Apple Watch - Apple Support
i.e. press and hold both the side button and Digital Crown for at least 10 seconds, then release both buttons when you see the Apple logo.
If you've completed that troubleshooting and the issue is still not resolved, Contact Support.
You also need to try another charging puck if you have not already. If you don't have one go here
Click here > Genius Bar Reservation and Apple Support Options - Apple
or
Click here > Contact - Official Apple Support
or phone numbers
Click here > Contact Apple for support and service - Apple Support
Whether 12 months applies depends on your country laws. In my country you have up to 6 years to claim. In USA I believe the 12 months is it, and you bought it on that pretext.