I had solved this by turning off Private Wi-Fi Address & Limit IP Address Tracking on the iPad but when I upgraded the IOS it popped back up again, even with those turned off. Was able to resolve it by kick starting the bluetooth connection between the MacBook and iPad - sent myself a file via AirDrop and Sidecar started working again.

[quote='777361022, MarkyS, /thread/675144?answerId=777361022#777361022, /profile/MarkyS'] Turn off "Limit IP address tracking" [/quote] WOW - All this time I have fought this and the solution has been right here since January