When your Tailscale account is linked, Screens ensures that Tailscale is installed and connected on the source device, as it is required to access your other devices.
In rare circumstances, Screens may be unable to detect Tailscale's presence. If this happens, a warning will be displayed:
If you are certain that Tailscale is installed and connected, you can click the Ignore button to dismiss this warning.
Otherwise, please ensure that Tailscale is installed and connected. Detailed instructions can be found in this article.