For Wired Keyboards:

Try different USB port. Test keyboard on another computer. Check for visible cable damage.

For Wireless Keyboards:

Replace batteries even if "new." Re-connect the USB receiver. Check receiver isn't blocked by metal objects.

Clean the Keyboard:

Dust and debris cause keys to stick. Turn keyboard upside down and shake. Use compressed air between keys.

Check Filter Keys:

Settings > Accessibility > Keyboard. Disable Filter Keys and Sticky Keys. These can cause unexpected behavior.

Update Keyboard Driver:

Device Manager > Keyboards > Update driver. Or uninstall and restart for fresh installation.

Try On-Screen Keyboard:

Search for "On-Screen Keyboard" as temporary solution. Helps navigate while troubleshooting physical keyboard.

Conclusion:

Batteries and cleaning resolve most issues. If specific keys don't work after cleaning, the keyboard may need replacement.