Right click the small speaker icon most likely located in the lower right screen corner.
First run the troubleshooter.
Second drill down through all of the tabs and properties within "Playback devices" and "Recording devices".
There are many settings available and hopefully you will be able to identify one or another as the reason.
First explore to see what you can find. Then go back and try some change but change only one thing at a time.
Keep notes in case you need to undo some change.