Best practice is to use MFA, but neither Google Authenticator nor Twillio Authy works...

Set up MFA on my root user account, per best practices. No problem in setting it up, but when I go to log into my account, it keeps telling me that authorization failed. The email address and password are correct (they work fine without MFA). I first tried using Google Authenticator, but I could not get into my AWS account. Finally deleted that. Downloaded and set up Twillio's Authy to use as MFA. Set up went fine. Logged out. Could not get back into my account. In both cases I tried resyncing the MFA to my account, but that did not work. Tried dumping cache data from browser, but that didn't work, either. This has happened on both latest version of Google Chrome and Safari, running on latest version of mac OS.

Having MFA is a great idea, but I have never had a problem with it on dozens of other accounts. What's the deal with AWS?