Good day to you,
If you are not getting a zig stitch or any zig zag pattern, when you select zig zag is the needle actually moving from side to side?, if it is then it may be as simple as a bent or blunt needle, this minor thing alone will cause the problem because the point of the needle is too far away from the hook, if the needle is not moving from side to side when you have selected zig zag, let me know.
ken
drivewithken@blueyonder.co.uk, July 2007