Hello,
1.If the audio was working recently, please try System Restore first by selecting a restore point from a date when the sound was still working.
2.If that does not resolve the issue, download and install the audio driver from the computer manufacturer’s support website.
If the manufacturer’s driver also fails to load, then either Windows itself is damaged or the audio hardware on this older PC may be failing.
3.Next, try a Windows 10 repair installation (in‑place upgrade):
Download the Media Creation Tool from Microsoft’s official website.
https://www.microsoft.com/en-us/software-download/windows10
Run the tool and choose to download an ISO file.
Open the ISO and run setup.exe.
Your apps and personal files can be kept, but please make a backup just in case.
4.If the repair installation does not change the situation, the audio hardware may have deteriorated.
In that case, using a USB audio adapter is the simplest solution.