I think it's only trying to give signals to the audio jack because when I ran diagnostics without headphones it showed it was testing headphones. It's a Intel, Toshiba, Microsoft. I've checked to see if it was muted, if the tab was muted, if the video was on mute, and just about everything like that.
1. Go to "Control Panel".
2. Click on "Sound".
3. Make sure you are on the "Playback" tab.
4. Click on the device you are trying to fix.
5. Now click the "Configure" button and follow the prompts. (Be sure you also click the "Test" button.)
6. Once that is complete, click the "Properties" button.
7. When you are done with your changes, in "Properties", click "Apply" and then "OK".
8. Then click "OK", again, on the main "Sound window".
You may also, while in there, want to update the driver to see if that resolves is.
If you are still only getting sound from the headphones, then I would consider having a tech look at the device (or the manufacturer if it is under warranty still).