When your screen is not being shared with all of the students during a live lesson on Microsoft Classroom, the following steps can be taken:

1. Check the screen sharing settings to ensure that all students have access to it.
2. Check to see if the video is paused on your end, or if video sharing is enabled.
3. Ensure that the ‘Start Live Session’ button is clicked.
4. Check for any technical issues with your internet or device.
5. Close out of the session and start a new one.
6. Restart the device.
7. Log out of Microsoft Classroom and log back in.