5250 issue - Mochasoft does not respond to ne application

All,

We use Client Access for 5250 emulation, but also have a license for
Mochasoft 5250.

We have one application, an old version of inventory management from Infor,
where Mochasoft doesn't work. The application simply doesn't respond, as
if the user hasn't done anything. I've never understood why and today
something just popped into my head.

Isn't there a way in 5250 that an application can handle function keys or
ENTER or whatnot by a different method? Called the Aid byte or something
like that?

I wonder if that's how this app is written and that's why Mochasoft won't
work and Client Access does?