The Google account is a few months old and the first keys were created last night i.e. about 12 hours ago. In the mean time I've deleted all of them and created new ones, for about 2 hours now, maybe even 3.
I get no error inside the B4A app, actually after clicking on my email address on the phone when signing in I get the "sending message to waiting queue" and "running waiting messages" in the log, but that's about everything. The label on the screen doesn't change text either.
And yes, the API is enabled: