I have a Sweet 16 too. Double check that you've threaded your machine correctly. I've found its easy to miss the take up lever
or something else, apparently obvious, but totally missable. Also make sure your bobbin is inserted in the bobbin case correctly, so that when you pull out the thread, with the bobbin facing you, the bobbin rotates clockwise. Check your bobbin area to make sure there isn't a stray piece of broken thread stuck in the bobbin race area. If there is, using the hand wheel, you can slowly rotate it while hanging onto the stuck thread and it should pull free at some point in the rotation so you don't break the thread a leave any behind. If you are not using coned thread, but spools that are not cross wound, your thread needs to be on a horizontal spool holder so it comes off the spool straight. This problem you're having is fairly common and I don't think serious, but a simple fix. Good luck! Let us know when you figure it out.
Kathy