I know how to use logic pro and how to find EZKEY'S in logic.
( Your customers are not obviously complete beginners)
But at this place I only can find EZDRUMMER Démo and nothing else.
EZKEY'S full version is nowhere after installation, neither in stand alone version, nor in my Daw.
Since you couldn't help me, I tried by myself to install EZKEY'S on an external hard disk with MAC OS 10.10. and it works perfectly.
The fact is that EZKEY'S installation go wrong with MAC OS 10.11.5 and you should say that and recognize it.
So what can I do know ?