I get an error message on the Google sign-in page when attempting to authenticate with my own credentials:

Something went wrong

Sorry, something went wrong there. Try again.

# From within my mail directory: ~/mail/<name>.<address>/
gmi auth -c ~/Downloads/client.json

This occurs on the latest release gmi, the latest commit (pipx install .), and the most recent commit which passed all tests (54c7201).

I've used these credentials in the past on another computer with success. I'll debug further tomorrow and post an update.