[albee1952]

Only thing I would guess is that Pro Tools is not "up front"(the program in focus). This might happen if the PT window is not filling the entire screen and you clicked somewhere outside of the PT window. Or is it an old keyboard that maybe has an intermittent space bar? Adding a control surface might be a solution worth looking into. This doesn't need to be anything fancy or expensive. The original Presonus Faderport is a dandy little helper at under $100 on the used market. Clicking off the PT window should not remove focus from the faderport(mine still controls PT even if I have another program up front).