So I got ride of my 500 and put a 750 with FIQ in my sprayer tractor.  The foot switch that worked great last year is not working this spring.  It's still plugged into the T2 right where it was last year.  I checked the switch with a continuity tester and it's okay.  I also tried setting the remote engage to "seat switch" and when I push the switch the screen still said "cannot engage, no one it seat".  My dealer isn't real sure what it might be either.  I'm running 4.0 in the 750.  Does the T2 need compatible firmware?  Would it have anything to do with the FIQ?  I have a foot switch in my other tractor with a 750 and ezsteer and it worked great last year.