Revolving around the core of technology
as a user, go to 2 factor link at the bottom of the page, select 30 second password option, scan the barcode, that works fine, save, logout, try to login, 2 factor will not allow login.
Please ensure the time on your machine is correct. I recommend letting the OS fetch the current time from a time-server. If the clock on the machine is even off by a minute, the code won't work.