I was also caught in a loop to update. I'm running 10.15.7
I think I tried 4 times to start the app, having it run through to update, but that didn't work. It worked after launching from the Terminal app:
open /Applications/TurboTax\ Home\ Business\ 2019.app
It still did that same start up to update, but then it finished. I was about to restart my Mac, but this worked. Sometimes a fresh restart will fix weirdness, this time it was not needed.
