The display issues with two-factor authentication should now be fixed - it seems some of the templates got messed up, causing these popups to render entirely white and thus not be readable by users. Some of the prompts may look quite messy for the time being, as I need to delve more into the template system to get the right colours applied to the right sections - but it should at least be readable now, so those using 2FA should be able to login again. Apologies for the issues, and thank you to those who reported it so it could be fixed.