why aren't my f5, f6, and f7 key not working

The actions associated to the function keys are not controlled by Windows, because the actions vary from PC to PC.

If the function keys (F1 - F12) are not producing the correct action, try pressing the Fn key + a function key to test if that produces the correct action.

If it does, press Fn + Esc to toggle the function lock off.

If that does not resolve the problem, boot your system into BIOS and look for a setting to toggle between Function keys and Action/Media Keys.

If your F5, F6, and F7 keys are not working to control the volume, there are a few troubleshooting steps you can try:

1. Check for Debris: Sometimes, debris under the keys can cause them to malfunction. Use compressed air to blow under the affected keys and wipe them with a slightly damp microfiber cloth.
2. External Keyboard: If you have access to an external keyboard, try connecting it to see if the volume keys work. If they do, it may indicate a hardware problem with your laptop's keyboard.
3. Safe Mode: Boot your computer in Safe Mode to check if the keys work there. If they do, a third-party application may be interfering with the functionality.
4. Audio Drivers: Ensure that your audio drivers are installed and functioning correctly. You can check this in the Device Manager. If necessary, update or reinstall your audio drivers.
5. Troubleshoot Audio: Run the "Playing Audio" troubleshooter from the Settings app under System > Troubleshoot > Other troubleshooters to see if it identifies any issues.

These steps should help you diagnose and potentially fix the issue with your volume control keys.

References:

• How to fix this. no audio device is installed - Microsoft Q&A
• My audio inputs and outputs suddenly disappeared, how do i fix this? - Microsoft Q&A