Check to make sure that your needle is completely inserted up into the machine, and that it is straight with the proper side towards you (just in case you don't know: the 'ditch' that runs from the eye of the needle all the way up the needle to the part that inserts into the machine, is the front of the needle).
Check to see if the needle is the proper size. A wrong length needle or a size that is much smaller than you had been using (say you had been running a size 18 and decided to go down to a 12 for finer fabric) will sometimes require resetting the looper because it isn't able to grab the thread because the needle is too far away..A mechanic needs to do that.
Last but never least, you may have hit the end of the looper and chipped the end. If you have done that, unfortuneately they don't heal them selves and you will need to............you guessed it!.....call your mechanic.
Once in a while, there is a rough place on your plate or the wire on the tension for that thread has a small groove cut in it from the thread and you would need a new wire in your tension,
Look at the needle problems first.If your machine was sewing fine before, it is probably the needle, If the machine is new to you, the other things could be the problem.
Answers & Comments
Check to make sure that your needle is completely inserted up into the machine, and that it is straight with the proper side towards you (just in case you don't know: the 'ditch' that runs from the eye of the needle all the way up the needle to the part that inserts into the machine, is the front of the needle).
Check to see if the needle is the proper size. A wrong length needle or a size that is much smaller than you had been using (say you had been running a size 18 and decided to go down to a 12 for finer fabric) will sometimes require resetting the looper because it isn't able to grab the thread because the needle is too far away..A mechanic needs to do that.
Last but never least, you may have hit the end of the looper and chipped the end. If you have done that, unfortuneately they don't heal them selves and you will need to............you guessed it!.....call your mechanic.
Once in a while, there is a rough place on your plate or the wire on the tension for that thread has a small groove cut in it from the thread and you would need a new wire in your tension,
Look at the needle problems first.If your machine was sewing fine before, it is probably the needle, If the machine is new to you, the other things could be the problem.
Good Luck, :)