One of the first things to check is to see if your F4 mic key is lite up. If it is, press fn + F4 which should make the light go away and fix the issue. If that is not the case check out these other solutions. 

The fix for this varies by win 11 and win 10. I will post screen shot solutions for both.

Win 11 Fix through settings.

To un mute your mic you will want to click your settings wheel icon.

Then click system, After that, select sound. 

Next you will want to select microphone array

If your mic has a line going through it just click the mic icon to remove the line and should now be unmuted.

 It should look like this once it is fixed.

Win 10 control panel fix.

More advanced solution. (It the next resolution seems difficult please create an IT Ticket and we would be happy to help.

Here are some screenshots on how I fix through control panel

Right click on the mic that show the green bars on the right and select properties. Depending on headphones or built in or external camera this could change.

If the speaker icon has a line through it click that icon and press ok on any open windows. That should fix it.