If the arm does not come down (with light pressure), there could be a couple of causes. First, the table may have been shut off, before the arm return finished its cycle. The cure for this is to turn the table on and see if it completes it, or start it out playing (no belt, platter wont spin), move the arm manually over where the record label (keep the stylus from damage) and see if the arm returns again on its own.
If that does not fix it, then there are linkages underneath that are out of wack. There is a return adjustment screw by the tonearm base, that adjusts when the tonearm lifts from the record at end of play. If this is set to early, that may also be another cause. That means linkage is still in cycle when the arm is in the return position.
Wayner