MBC Storm Door Mortise

I'm afraid that I don't know what handle set the MBC door was meant to use. I'm not familiar with that brand. That said, I don't think your handle set is for a sliding door. This looks exactly like what you'd see on a commercial swing door. The hook deadbolt is made so that when it lathes onto the keeper, it can't be pried open.

If the only issue is that the hook is sticking, then my guess is that the keeper needs to be adjusted, or the door might be out of line with the jamb. My first suggestion would be to check those details to see if that might help the issue.