can't use the keyboard volume button on my laptop..

Perform these checks and fixes in order:

1. Test volume in Windows
   • Select the Speakers icon on the right side of the taskbar.
   • Try changing the volume with the mouse.
   • If this works, the audio system is fine and the issue is with the keyboard or its special keys.
2. Use the on‑screen and hardware volume controls
   • Use the physical volume button on the device (if present) to raise or lower volume.
   • If using a Surface Keyboard or Type Cover, use the top‑row volume keys (speaker with minus/plus icons). These keys control volume when the Fn light is off.
3. Check if function (Fn) mode is enabled
   • On Surface keyboards, the top row can act as either special keys (volume, mute, brightness) or F1–F12.
   • Press the Fn key once to toggle modes:
     • Fn LED off: top row works as special keys (volume, mute, etc.).
     • Fn LED on: top row works as F1–F12 and will not change volume.
   • Make sure the Fn LED is off, then try the volume keys again.
4. Update Windows and device drivers
   • Go to Start > Settings > Update & Security > Windows Update.
   • Install all available updates. This ensures the latest keyboard and special‑key improvements are applied.
5. Check keyboard behavior and special keys
   • Go to Start > Settings > Devices > Mouse (and Typing if needed) to review input settings.
   • If using a Microsoft keyboard, install and use Microsoft Mouse and Keyboard Center to customize key behavior and confirm the volume keys are mapped correctly.
6. If audio itself doesn’t respond to volume changes
   • Confirm audio devices and drivers are working:
     • Open Device Manager and verify audio devices are present and without error.
     • Update or reinstall audio drivers from the device manufacturer if needed.
   • Run the Playing Audio troubleshooter from Settings > System > Troubleshoot > Other troubleshooters.

If the volume works via the taskbar slider but never via the keyboard, and Fn mode and updates are correct, the keyboard hardware may be faulty and may require service or replacement.

References:

• Surface sound, volume, and audio accessories
• Special keys and function keys for Surface Keyboards or Type Covers
• Use the special keys on Surface Keyboard
• Troubleshoot problems with your Surface mouse or keyboard
• How do I use the Fn key/F Lock key/Alternate command keys?
• How to fix this. no audio device is installed - Microsoft Q&A