I encountered the missing security icon issue on a couple of laptops I worked on recently. After doing a search, I found many others have had the same problem so I'm posting this simple fix.
1. Open Task Manager.
2. If there are no tabs showing, click 'More Details' at the lower left.
3. Click the Startup tab.
4. Find 'Windows Security notification icon' on the list, click on it to select, then click 'Enable' at the lower right.
5. Close Task Manager.
5. Restart the computer.
Last edit: 16 Feb 2021 21:25 by riider. Reason: Edited for clarity.