Apple Watch stuck on basics after update

Gen 3 watch. Watch iOS is 7.5. Phone iOS is 14.6.

I didn't have any issues with my watch until I had to update the software after installing Spotify (to use offline). So I updated the software and now it is stuck on the basics screen. I have used the reboot feature and power off, but it comes back to the basics screen. I have also paired it several times. At this point I may return the watch to the seller (got it off eBay). I have read some other suggestions, but none seem to work. Randomly it will look to pair and then say it's not paired, but I've paired it several times. Thinking maybe just keeping it next to my phone for a day may help. Thoughts?