I’ve never had this with Etap but I’ve had issues with Di2 dying after a firmware update.
I would try this:
#1 remove both batteries, charge them fully, then reinstall them.
#2 delete the app from your phone and reinstall
#3 re-sync the app with the groupset.
#4 re-install all firmware (overwriting existing).
If all that doesn’t work, I’d be taking it to a dealer.
Hopefully someone with more SRAM knowledge can chime in!