Can't get Apple Watch to unlock iPhone

I have an iPhone 13 running iOS 15, and an Apple Watch 6 running watchOS 8.0 Since upgrading, I can't use my Apple watch to unlock my iPhone. It keeps telling me that I need to wear my watch and unlock it (I'm doing both) and unlock the phone (also true). It all worked fine until I upgraded to both iOS 15 and watch OS 8.0 and got the iPhone 13 (all at the same time).