My iMac has stopped unlocking with my Apple Watch. I have scoured the internet for solutions and implemented everything I can find (including deleting Keychain entries, plist entries etc), short of deleting the watch and repairing it which seems drastic.

None of the solutions make any difference. Every time I go to Security & Privacy and try and check the Unlock with Apple Watch box, the message "Your Mac was unable to communicate with your Apple Watch" comes up.

It's very frustrating and very 'un-Apple'. Has anyone else experienced this?