AKAI MPk25 only some keys play sound with plug in VST
 

I have Pro Tools 12 and an Akai MPK25 that I'm using to control MIDI.
PROBLEM: only certain keys play sounds when in Pro Tools with a VST.
Here's a video of it:
[URL="https://www.youtube.com/watch?v=ybEqctKQsV4"]https://www.youtube.com/watch?v=ybEqctKQsV4

Anyone know what this issue is and how to solve?

Much appreciated. Really. MUCH appreciated any help!