Hey guys, here is the problem.I import my FS Flight Plan to the FMS, no problem with that, when I take off y turn on the AP and try to change the HDG to the NAV, wich it doesn't.Why I can't change it to NAV? Everytime I push the button I stays in HDG.PLEASE HELP!

If you have correctly configured the MCDU then the aircraft will automatically go to Managed Navigation while still on the ground (HDG Window will be dashed) if you don't see that then check you have entered everything correctly. First thing that comes to mind is a Discontinuity also do you have the F/D switched on?Regards