When trying to pair my series 4 watch with my iPhone 7 it says I need to update my iPhone, but I already have the latest iOS?

I recently received a hand me down series 4 Apple Watch. While attempting to pair it with my iPhone 7 I get a pop up stating my phone is out of date and I can’t pair the watch until I update my phone. When I go to my settings, though, my phone says it’s up to date with iOS 15.7.1. I’ve tried resetting the watch and restarting my phone, but I’m still getting the same error message.