Apple Watch won't unlock Mac after iOS 18/macOS Sequoia upgrade

Didn't log out of anything, but did unpair and re-pair my watch (and repaired boot drive in Recovery -- some snapshot errors there). Restarted, and neither watch nor Touch ID (that was new) would work -- at first -- but both became functional after maybe an hour had passed -- possibly an iCould synch issue there.

The problem is that when Apple changed from so-called Apple ID to Apple account something got messed up. The solution is to log out of Apple ID/Apple account on all your device devices and log back in the one complication is you need to unpair the Apple Watch from your iPhone and then pair it.

Long story short me too, I toggled bluetooth etc etc etc. Unpair the watch from the phone and then re-pair. this is relatively painless but will suck up 30 mins has the unpair back up the phone and watch to cloud, wipes the watch reinstalls and then you have to add all your credit cards to wallet on both the phone (why?) and the watch (obviously). The wallet part was confusing. Do NOT use the CVV security code that it somehow remembers. Type the 3 digits in by hand. Instally the Mac, not obiouvly involved in any of this recognizes the watch.

Same story with my Apple Watch Series 6 and my M1 Max Mac Studio. Watch, iPhone 15 Pro, Mac Studio all updated to latest versions of software. If I toggle the control to enable Apple Watch unlock the Mac, I get a spinning wheel.

Deleting the plists in System/Library/Sharing/AutoUnlock resulted in, after toggling Apple Watch back on in System Settings, a window that first asked for my password, then reported "Your Mac was unable to communicate with your Apple Watch...".

I get the same issue. I'm using an M1 Mac Mini and an iPhone 15 Pro Max and an Apple watch series 8. I didn't upgrade to Sequoia yet but I upgraded to iOS 18 and Watch OS 11.