last week I looked at a friend's old singer which was not working. I began by putting all levers into correct positions. Began to sew missing stitches. Cleaned bobbin area and changed thread. Still sewing but skipping stitches. Each check was a slight improvement. Finally tried to take needle out, pliers required, kept pulling. Eventually another lady took it out stronger fingers than mine. New needle and it worked. Friend had lent the machine to someone who maintained he had not fiddled or taken the needle out. Finally he admitted he had. The needle we worked out was not in the needle shaft so we sewers knew it had been moved. Would have started with needle had I known this fact.
needles need to be new and in the shaft to work properly. Hope you keep sewing.