The iPhone 13 lineup launched earlier this month. And, unfortunately for some new owners, a bug surfaced that caused the new hardware to not properly communicate with a paired Apple Watch to access the ability to unlock the iPhone 13 with an Apple Watch. This feature is designed to make unlocking an iPhone with Face ID much more streamlined while wearing a mask (but it works without a mask, too, like when wearing certain sunglasses).
iOS 15.1 beta 2 fixes bug causing issues with unlocking iPhone 13 with Apple Watch