re; garter carriage?

many thanks for your answer I will check the plug,however my son has had a look for me and it seems that the back of the carriage on the left side (where the plastic bit that the row tripper goes )dosent seem to be connecting some how with the rail of my machine to go across, almost like its not weighted or heavy enough if i apply some pressure with my hand it works ,the minute i take my hand off it stops, obviously i cant hold it down the whole time . I dont know if that makes any sense or if youve heard of it at all im wondering if ive been sold a faulty machine.Regards Debbie