Well, sort of. I changed my user language, in my profile from en_US back to en_GB.
Now my two-factor and user invitation plugin display properly.
But, why did my user profile language change? I do not recall changing it. Maybe I did at some point and I just do not recall. The last plugin I installed prior to today was the nodebb-plugin-newsletter to test it for the developer, in another thread.
I un-installed that plugin and it did not make a difference but that is when I noticed my user profile language was set to en_US.