1
Press each of the Alt keys on your keyboard, to test if one of those keys opens the Windows Start Menu.
If one of the Alt keys does open the start menu, the solution may depend on your keyboard, try each of the following keyboard shortcuts one at a time to see if that switches those keys back:
Fn + A
Fn + S
Fn + Spacebar for 3 seconds
Tap the Windows key twice
2
If that was not the problem.
Open Command Prompt, then paste in this command and press Enter:
msdt.exe -id KeyboardDiagnostic
Run that Keyboard Troubleshooter to see if that can solve the problem.
.
If the problem is still not resolved:
Connect another external keyboard to your system, is the same problem occurring on that keyboard?