You could rebuild the tension but I think first if it were me I would look in the manual and see how to put the thread through it - I can see that you missed a step. If you do take that one apart, unless you get that tension back the way it is supposed to go it won't work. If you don't have a diagram of how it should go and someone already tried to rebuild the tension that could well be your problem. You may have the best luck buying a new tension for about $15 more or less and just simply replacing that one. I don't know of any diagram for rebuilding that one. Replacing that tension might only involve one little set screw. Don't throw out the old tension - parts are nice to keep around.