Thank you! I really hated to toss this beautiful device which continues to represent the unmatched low-cost precision manufacturing of Japan. How could it just stop working. Thanks to your tips, I used a jeweler’s loop to discover the battery lid metal contact (which appeared fine to the eye) was completely brown. Strange, there was never a leak, but somehow it corroded. Perhaps humid bathroom storage. Anyway, a little filing down, pulling up on the springs, and it’s working again!
FYI my used Mac didn’t have the bracket or screws. 3D printed the bracket someone did (it’s on Thingiverse), M2x10mm screws were short but worked.