If you can't get the needle to pick up the bobbin thread you can't sew.
Even though every sewing machine has a different threading path and process, if the sewing needle won't catch the bobbin thread, you won't be able to sew. A sewing machine works by locking two threads together; the upper thread is carried by the needle, while the lower is carried by the bobbin. If your machine is running, but the needle simply won't pick up the bobbin thread, there are a few techniques that may solve your problem and save you a trip to the repair shop.
Needle Unthreaded
It sounds silly, but the first thing to check is your needle; it must be threaded properly to pick up the bobbin thread. Pass the thread through the hole in the needle from front to back, or as directed by your sewing machine manual. Turn the wheel of your sewing machine away from you to slowly dip the needle into the bobbin case and pick up the bobbin thread. If the thread still won't catch, consider another cause.
Poor Bobbin Threading
No matter what brand of sewing machine you have, the bobbin thread will have to follow a specific path to be picked up by the sewing thread. If the bobbin is paced incorrectly, or the thread isn't inserted in the correct slot, there will be no way for the sewing thread to pick it up. Remove the bobbin, check the manual for the proper thread path, and replace the bobbin in the correct slot. If your bobbin needs to go into the machine with a specific side facing up, add a dot of colorful paint or nailpolish to the right side of the bobbin casing and you'll be able to install it correctly by simply looking for the marking.
Tension Issues
If your machine tension is too loose, the sewing needle won't be able to pick up the bobbin thread, even if it is passing through the correct area. Loosening the sewing tension one number at a time until you are able to retrieve the bobbin thread will resolve the issue if it is tension related. If your sewing tension is too tight, one or both threads will break each time you try to sew. A good indication of a tension problem is a tangle of loose thread wrapped around the bobbin casing. If you open the casing area and see this, then tension is likely the culprit.
Mechanical Issues
If checking the bobbin, needle and thread tension don't yield a solution to the problem, then the issue may be a mechanical one. If your machine has recently been damaged or dropped, or if you have done some home modifications, a trip to the sewing machine repair store may be required. If you need to bring your machine in for service, bring along any related parts and a sample piece affected by the problem if you have one. In some cases, you may have been working on a project when the problem occurred. Bringing along the project can help the repair person diagnose the problem.
