This has been an ongoing problem with just about every macOS upgrade or update. The solution in my case has usually been to wait a day or two... until one day even that didn't work.
The following Discussion describes the procedure I used after waiting a few days with no resolution:
Can't unlock Mac with Watch since Ventura… - Apple Community
Try it. Forget about deleting Keychain entires etc. Same goes for un-pairing, re-pairing, signing out, signing in... I tried all that and more. Nothing worked.
As a perfunctory prerequisite be sure to follow Apple's steps first, as I recommended in that Discussion, but which didn't work for me: Unlock your Mac with your Apple Watch - Apple Support.
Yes this has been beta tested as well as reported, but given its (usual) spontaneous resolution after a day or so it has failed to rise to the level of requiring attention from Apple... yet.
My next move is to contact support…
Definitely contact Apple and tell them about it. It shouldn't require the conniptions I described in Can't unlock Mac with Watch since Ventura… - Apple Community.