You have to be withing 5 degrees of the route before the IRS will lock into the autopilot. You either did not select a SID (Standard Instrument Departure route) or you went too far off the Flight Plan before engaging LNAV and VNAV OR you have a discontinuity in your Flight Plan (make sure you select the next LEG in the flight plan after the DISCOUNTINUITY boxes then paste that leg or type it into the DISCONTINUITY boxes). Fly VFR until you are within 5 degrees of the Flight Plan and then retry engaging CMD and then LNAV and VNAV. You should feel the autopilot taking control at that point.

-=RenSpur=-

Confucious say, "Duck who fly upside down bound to have quack up."