You must have a setup for the type of mod you are using inside that track's folder for that mod to load the track.
So if it's
cup, nscs10, cup10w, sprint_cup, etc... = fast.cup.sim
gns, outlaw lm, lmv2, etc... = fast.gns.sim
cts, ncts09, gn69st, gn70ss, snsc70, etc... = fast.cts.sim
pta, trans-am, etc... = fast.pta.sim