"Add Display" drop down button missing

As picas said: if your mac does not see another device, the button won't show.

You need to make sure that:

both your mac and the other device (iPad, or Apple TV) are on, are connected to the same Wifi network, Bluetooth is on, and they are logged in to the same Apple ID.

I have finally Solve this issue in may case. It was a matter to activate icloud connection on my mac. After I did that the add display button appeared and was able to tick the last box on the universal control of "Automatically reconnect to any nearby Mac or Ipad". Try this and maybe you have same luck as I did.

Best

Try booting into Safe Mode then reboot normally.

How to use safe mode on your Mac - Apple Support

If your Mac can't see the display then the option will not show. You should try and reconnect it: Connect a display to your Mac – Apple Support (AU)

After countless calls to Apple Support, with an EXTREMELY helpful agent by the name of Robert we were still facing the same issue. Then randomly one morning randomly I was prompted to log into my iMessage on my iPad. Instant success.

All is working seamlessly.

Best,

My add display option was missing , I can't use neither universal control and sidecar after updating to the newest version on both MacBook and iPad. I tried the solution provided above, it doesn't work at all. Sigh><

Hi all,

Same issue, updated to latest version of Monterey. Bought a M1 12.9 iPad solely to use with my Macbook Pro with universal control, and sadly no game. Spent close to 2 hours on the phone with Apple support yesterday and they could not solve the problem.

Very annoying...

I will follow-up if they solve the issue.

Kyle

Hi, Bro. I have the same problem. Do you find the solution to it?