First off if you haven’t been to the Play Store from your watch before it may not register your watch as a device.
Go to play.google.com and see if it comes up on a search the watch faces take longer to be seen than the Android apps in the Play Store.
If you don’t see your watch face listed in Play Store watch section search then search this forum for other Play Store issues there are some settings you may have missed. Here is one link to try.