I think they are having issues with anyone who selected the option to not bother them for 30 days with the 2nd login verification.  Instead of telling you there is a problem, it just endlessly asks you to login and fails.  It should just have you do the 2nd step when it can't verify your identity using old cookies.   Hopefully, they will fix this on their website.

The workaround is to delete your coinbase cookies and refresh the login page.