Mac not unlocking with Ultra Watch (yet again)

Once again, my Ultra Watch isn't unlocking my Macbook Pro (2023) like it usually does. This problem seems to pop up fairly regularly, perhaps every 2 months or so. Usually it's just a matter of restarting the watch and it starts working again - tedious, but it works. Sometimes I have to jump through a few more hoops - there's a solution posted here previously that involves deleting entries in Keychain Access.

Today however, none of that is working. System Settings>Touch ID & Password, in the Apple Watch area, The toggle won't stay on, no matter what I try. I just get the stupid "Your Apple Watch must be signed in to iCloud to allow it to unlock your Mac." It IS signed in. I've tried restarting everything involved. I've tried deleting those entries in Keychain Access and Library. My Mac, my iPhone and the Watch are all updated to the latest firmware versions.

Are there any other solutions to this?