I have no problem sending or receiving MIDI on my GX76 from my laptop computer using a USB MIDI interface. It worked right out of the box... I was able to play a demo song to my laptop computer. And then play it back to the GX76 keyboard.

You should check your MIDI cable connections, or you might have a defective unit.

IMHO, PSR-GX76 is a super bargin at less than $400 USD. It has 76 keys, 2-way speakers, 64 notes poly and some pretty good sounds. I used it in a few live shows and it sound good. There is some noise so it's not good for studio work.