Hi Debbie,
Does the motor work if you switch it on when it is off the knitting machine or do you still have to put pressure on it?
If you still have to push on it, it suggests a loose connection inside the garter carriage. It is possible to lift the cover and see some of the works - I've done it! Perhaps you may find the problem that way.
If not there are still a few places that repair machines and their attachments and a Google search will give you a few to choose from.
I do hope you manage to get it working.
Regards,
Sue, March 2011