I have no idea why it won't track the route for you. I have had nothing but success with the L-1011 tracking routes.

INS
Mode Selector Knob - NAV (set after alignment, and when the Ready NAV light turns green)

Autopilot
FD Swithes - ON
HDG Switch - ON
Navigation Source Selector Knob - FMS

In the attached image, it shows all that is needed for the route loaded into the INS to be tracked (the INS on left side of the image shows the Ready NAV light is green, so the Mode Selector Knob, on the INS, can be now be rotated to NAV).

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