Here is the steps to check if your laptop web cam is working: 
Step 1: 
1: On your laptop, click on the Start Menu and type in Settings, click on Open. 
2: Click on Apps, Installed Apps and look for Microsoft Teams in the list 
3: Click on the ... and select Advanced Options
4: In the Menu, make sure that Camera and Microphone is set to ON. 
5: Close out of the Settings Window. 
Step 2: 
1: Open up Teams and click on Settings (You see 3 dots next to your profile pic).
2: In the Settings menu, click on Devices and scroll down to Video Settings. 
3: Check that your Camera is set to LG Camera (You may see other plug-ins listed). 
4: You should now see the preview screen show your laptop web camera.