It might be worth spending some time on this website: https://bettershifting.com the author of which is among us.

I had a bit of trouble following with all of the passive voice, but did you get a new battery and find that it still didn't work, or are you just curious why the old one doesn't work?

Also, is the battery recognized by the E-tube software? If so, you might be able to correct the problem by forcing a firmware update.