PBS playtime tablet all of a sudden stopped making any sounds.

If you are sure that your headphones are not the problem, then there must be a software/hardware issue with the tablet itself. ... By restoring your device, you make sure there is no software issue with your device. If the sound still does not work, try replacing your audio jack.
I looked everywhere for an answer and tried it ALL, from cleaning the jack port, reboot, restore to fabric options, and many more, but none of them worked. However, as I was trying not to go crazy trying so many weird things on my new not properly working tablet, I accidentally found the solution!!! why it works I don't know, but it does so here it goes:
1. Turn device off
2. Make sure your headphones are plugged ALL the way in (you should hear a click sound)
3. Press the on/off button and the volume up button at the SAME TIME
4. Once the screen is on let the on/off button go
5. DO NOT let the volume up button go
6. Wait until the tablet has finished loading all settings up.
7. Let volume up button go.
Problem should be fixed now. Enjoy