I hope you have removed the shifter from the transmission or it will not move back far enough to get to the clutch. If you have then check the clearance between the body and bellhousing/transmission for room to move. And if everything is ok and the shifter is out and you have plenty of room then its prob stuck in the clutch disk and jest needs a good shot of WD-40 on the input shaft and parts (as best as can be done) and a firm tug.
Good luck