Open up the bottom of the machine. It's possible you have some thread caught in there too. Also, make sure there is absolutely no little bits of it left in the bobbin assembly. It may have to come out to get all the thread. It's held in by two, spring loaded screws. I've worked on several of these machines and they're wonderful. You do need the correct bobbins or you'll have nesting. This machine does not take plastic bobbins. You can find the correct bobbins by doing a google search.