I am a novice here, but I have a Free #5 treadle also. Have you tried to watch what is happening when you make a stitch? In other words, take off the front slide plate and then turn the hand wheel to make sure the thread is going down and making a loop for the shuttle. Also, I found that I had to put the bobbin in a certain way for it to feed properly...unfortunately at this moment I can't remember which end was up, as the saying goes. Maybe someone else here can assist further. Also, is your needle in correctly? This one is flat side to the right, threaded left to right.
HTH,
Jp