If you're wondering why you can't unlock your iPhone 13 with the Apple Watch, you're not alone. There's a bug that affects the new iPhones from using the feature. Apple released this functionality to allow users wearing face masks or sunglasses to unlock their smartphones without Face ID or passcode. But some users trying out the feature on the iPhone 13 are getting error messages like "Unable to Communicate with Apple Watch," or they can't set it up at all.
For some reason, it only affects the newest iPhones, with older models working fine. Well, at least the iPhone X and later and Apple Watch Series 3 and later, since those are the devices that support this feature.
There isn't a quick fix from Apple right now. But some users claim they needed to reset both devices to get it to work. As Gizmodo pointed out, that seems like too much trouble to get this feature to work. Apple has said it is working on a fix in a future software update. So, for now, you'll have to do without it. To turn off the Unlock with Apple Watch feature, go to Settings > Face ID & Passcode.