why cant i turn the balance wheel?

Hello Adrienne,
Chances are there may be thread stuck in the bobbin case area, force the balance wheel backwards and that may free it off, failing that take out the bobbin case and see if you can see any thread jammed, a model number will help, you should find this just below the stitch length lever or dial, e-mail me.
Ken

drivewithken@blueyonder.co.uk
September 2008