Janome MC 9000 Embroidery/Sewing Machine

Question

My Janome MC 900 has a problem that when I touch the up/down needle button to bring up the bobbin thread, it shuts off. Won't sew another stitch. Have had it at a Janome dealor and he said that he fixed it, but when I got home with it, still same problem. Help!!
What happens and how can I get help?
I bought it new in 2000. The dealer that I bought it from is no longer in business.