Quiltersew - is your machine the 1600P, or the 1600P DB? If it's the DB, you should be using round needles, meaning they don't have a flat side at the top of the needle. And these needles HAVE to be inserted into the machine correctly. They have to be threaded from the side, not the front.
As I said, my machine doesn't have a needle threader, but I have other machines that do, and as other posters have said, the needle needs to be in the proper position and the presser foot needs to be down. Does your manual say anything about the presser foot?