IPad – Sidecar not working between MBP 15′ 2019 and iPad Pro 9.7′

The router IP might not be http://192.168.0.1

On your Mac go into System Preferences and select Network then Wi-Fi in the left hand list.

Just under the Status: line it should tell you your current IP address, make a note of it.

At the bottom right click on Advanced. Now select TCP/IP and Configure IPv4: should be set to Use DHCP. This pane will also tell you your router address a little further down.

Now you can point your browser to the correct IP address for your router and see what it is saying.

You can also open up Settings on your iPad and go to Wi-Fi then click on the little 'i' in a circle icon and it will tell you the IP address it is using and the address of the router.

If the IP address being used by both is the same then there's your problem.

First thing I'd check is whether the firewall is enabled on your Macbook and blocking incoming packets. If the firewall is on, try turning it off temporarily for a few minutes to see if the AirPlay icon appears in the menubar.

Next thing to check is whether the devices are on the same subnet. You can find the IP address and subnet mask of your Apple TV in Settings -> General -> Network. And the IP address and subnet mask of your Macbook in System Preferences -> Network -> Wi-Fi -> Advanced... -> TCP/IP. Ideally what you should expect to see is the same subnet mask on both devices (likely something like 255.255.255.0) and IP addresses that are similar except for the number after the last dot (something like 192.168.0.125 and 192.168.0.138).

Those are the two things I'd check first. Check those and let us know how you get on.

Apple have a guide to trouble-shooting AirPlay problems for Macs. There are a few other things that might help too: About AirPlay Mirroring in OS X