• The upper thread could be tangled.
  Remove the thread completely from the machine. 
  The correct size spool cap should be used for the size of the thread spool.
  Re-thread the machine according to the directions in the manual.

One Point Advice   Place a spool of thread on a spool pin. 

One Point Advice   Upper threading 

• Remove the bobbin and make sure the bobbin is threaded properly in the shuttle race. 
  Remove any loose threads or lint in the shuttle race.

One Point Advice   Installing a bobbin into a bobbin case 

• You could be holding the needle thread too tight.
  Hold the thread lightly to keep the end from going down into the shuttle.
  
  
• The needle could be thread incorrectly.
  Thread the needle eye from the front to the back.
  
  
• The needle could be bent or improperly inserted.
  Install a new needle with the flat side of the needle facing the back.