Apple Watch Series 3 Not Pairing

Hello,

I want to pair an Apple Watch Series 3 (WatchOS 8 something) with my iPhone 7 Plus (IOS 15.8.5). I go through with the pairing, but right when the iPhone app gets to the part where you press Get Started, the app crashes. When restarted, the Apple Watch goes back to the pairing menu and the app says "Unpairing Watch" and it unpairs with no trace of the watch.

This seems very odd, because the watch is visible under my Apple account. When I remove it and try again, same thing happens.

I realize that these are old devices, but it should work, right? They don't have compatibility issues with each other.

Any help is appreciated.

Thank you.