Possibly other WMF wikis too, but every time I try to input the TOTP code in mediawiki.org, I get the error message that it failed to validate two-factor credentials. I was able to get in with a remembered account on a different browser and disable 2FA using a scratch code. Attempting to re-enable 2FA results in the same message on the screen that has me enter a code to validate.
I've verified using both my regular app as well as a separate library on a separate device that the codes I'm typing in are correct. Can you please investigate why the server-side is believing the codes are wrong? My initial guess is a badly-synced clock on the server.
Feel free to poke me in freenode IRC #mediawiki (nick: Skizzerz) and I can help troubleshoot things further on my end as well.