Brother Sewing Machine Not Working (Ringwood BH24)

This machine has had very little use and looks brand new. However, despite it previously working like a dream, when I tried to sew with it last week, it had completely seized up. I took it to the Repair Shop in Ringwood on Saturday and three of their volunteers were unable to even get the case apart to solve the problem. Is there anyone with a knowledge of sewing machines who would like to have a go at finding the fault? It seems a shame just to dump it.