Are you having trouble with Sidecar not working?
I mentioned recently that my Apple Thunderbolt Display died. I’m currently waiting to check out a possible replacement, and in the meantime using my 12.9-inch iPad Pro as a second monitor using Sidecar.
It’s been a surprisingly usable interim solution, but I have hit a couple of glitches along the way…
Googling for solutions to these shows that I’m not alone, so I thought I’d share a couple of quick fixes I’ve found.
Using Sidecar for the first time
If you haven’t yet used Sidecar, you first need to make sure your devices are compatible. You can find full details of compatible Macs and iPads here, and you need to be on the latest major OS release for each, namely macOS Catalina on your Mac and iPadOS 13 on your iPad.
There are three different ways to activate Sidecar. The simplest of these is from the 
or 
icon in the top right corner of your Mac:
Read more at 9to5Mac.com