In order to use the screen share feature, you must ensure that you've enabled screen sharing permissions on your computer.
On your Mac, choose Apple menu > System Preferences, click Security & Privacy, then click Privacy.
Select Screen Recording.
Select the checkbox next to an app to allow it to record your screen.
Deselect the checkbox to turn off access for that app.
Select Start > Settings > System > Projecting to this PC .
Under Add the “Wireless Display” optional feature to project to this PC, select Optional features.
Next to Add an optional feature, select View features, then enter “wireless display.”
Select the check box next to Wireless Display from the list of results, select Next, then select Install.
After “Wireless Display” is installed, select Back to manage your projecting preferences on the Projecting to this PC page in Settings.
On the PC you’re projecting to, launch the Connect app by entering “Connect app” in the search box on the taskbar, and selecting Connect in the list of results.
On the device you’re projecting from, go to the screen mirroring settings (sometimes called cast settings), and select your PC to connect to it. If you’re projecting from a PC, you can also select Windows logo key + K and select the PC you’d like to connect to.