Just hooked up my LG monitor to my MacBook Air 2020 using the USB see to digital AV multi port adapter and it’s not working. I can see my desktop on the monitor but none of my files are showing up, or my applications. WTH?

Actually Tiffany, it is working since you see your desktop on the external display. You are probably using the external display as well as your MacBook Air's display. Please review the information below and it will help you get your external Display fully functioinal.

Use extended desktop mode

1. Choose Apple menu  > System Preferences, then click Displays.
2. Click the Arrangement tab.
3. Make sure that the Mirror Displays checkbox isn’t selected.
4. Arrange your displays to match the setup on your desk. To change the position of a display, drag it to the desired position. A red border appears around the display as it's moved.
5. To set a different display as the primary display, drag the menu bar to the other display. The primary display is where your desktop icons and app windows first appear.
6. 

Mirror your displays

1. Make sure that your external display is turned on and connected to your Mac.
2. Choose Apple menu  > System Preferences, click Displays, then click the Arrangement tab.
3. Make sure that the Mirror Displays checkbox is selected.
4. 

Axel F.