Touchscreen works keyboard doesn't

Hello. Both my sons got the 2 in 1 Viking Pro tablet this Christmas. The touchscreen keyboard works on 1 of the tablets but the keyboard stopped working? When I detached the keyboard and put it on my other sons it works and his is fine. I tried putting his keyboard on the one not working still same. Not understanding why this happened. I've researched and powered off and did HDMI thing. Need help