Earlier this spring, my 9 sp. flight deck quit picking up wheel speed too, everything else seemed to work fine.

Yesterday (yes, literally) I finally got around to trying to figure it out, and got it to work:

Looked at magnet/pickup position, seemed fine.

Removed magnet and just looked at it and made sure it was still a magnet.

Took off the computer head and sprayed the contacts on the mount and the computer head w/ electronic spray (I have a can for some reason), and scrubbed with a clean toothbrush. They did look a little grungy, but nothing that would make me take notice. I just cleaned it for the heck of it.

Put the magnet back on, realigned and everything works fine, so far. Haven't ridden any distance yet. So, I guess try cleaning the contacts?

Other than that, check ebay and online sellers for pickup/mounts. I found some computer heads on ebay a couple of years ago and bought a spare head, and mounting bracket on icyclesusa.com for a reasonable price (just looked there and they have 6500 - 9 sp - mount/pickup assembly for $28.