A coworker was having an issue logging into a website that requires two-factor authentication. We keep the authentication information for this site, including the TFA code, in a corporate 1Password account.
While he was getting his TFA codes rejected 100% of the time, I was having no troubles, using the same account, same 1Password, etc.
His system clock on his PC was running two minutes slow.
TFA codes are time-sensitive: the time is one of the factors in their generation (that’s why they expire every minute). If your system has the wrong time, your 1Password will generate the wrong TFA code.
The solution: he set his PC clock to the right time.