Yeah, thanks. That got me past the issue.
I probably didn’t need to do all of the following steps but it’s what I did… and the code is back on the primary login, without needing to re-register anything (pre-existing code works fine)…
As suggested, I renamed the “google-authenticator” folder under plugins to “google-authenticator-old”.
Logged in as normal (without 2FA).
Re-enabled the plug-in.
Under Settings\Google Authenticator, “Two Screen SignIn”, unchecked “Ask for authenticator code on secondary login screen”
Logged out.
I renamed the underlying “google-authenticator-old” folder under plugins back to “google-authenticator”.
Logged in again as normal (without 2FA).
Re-enabled the plug-in again.
Under Settings\Google Authenticator, ensured that “Ask for authenticator code on secondary login screen” was still unchecked.
Logged out.
At the primary login screen, the “Google Authenticator code” field was back… and I could log in without issue.
Thank you for the time and assistance. Much appreciated.