I was trying to log in into wikitech from my new phone today, I then got the message:

Login error
The two-factor authentication token provided was invalid.

I luckily still had a valid session on my laptop, so I looked up my settings, and 2fa was enabled. I have never activated it, this must be a side effect of the recent 2fa changes for the labs infrastructure. Switching it off of course doesn't work, this requires a 2fa token, which I don't have.