Opening the cartridge revealed the problem. The
battery (a solder-tab style
 CR2032) was actually good, but the positive terminal 'tab' had come off.
 The spot-welds just let go. It must have been poorly made, and then got
 dropped at some point. I don't have a replacement battery with solder tabs,
 nor do I have a way to get one quickly. But, this seems simple enough, I'll
 just solder the tab back on. 
I've *never* thought this to be a good idea.  I will either get one with the
tabs on it,  or put a holder in there,  or make some other arrangement...
Lots of the musical gear I used to work on for a living had such batteries in
it.  And they needed to be replaced after a while.  I'd usually put a holder
in there,  if at all possible,  and get some happier customers in the
process.  :-)
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin