Had another go at Nicole's CGEM mount. I was unhappy with the previous results.
Cleaned the board-ribbon cable contacts. Used some of the special nasty goop from the new tube of MG Chemicals Carbon Conductive Grease. Buttoned everything up including the black plastic washer for the power connector. Booted it up. OK.
Set it to track on Denebola. Set an alarm to check in a few hours. Should be at the meridian 'round midnight.