I just solved a mystery
I just solved a mystery! For weeks, my authenticator app wasn't working. It turned out that I had somehow fatfingered my phone's time settings so that it wasn't automatically trueing up its clock with NTP, and was gradually losing a few seconds every week. Yesterday, I noticed that my phone was 3 minutes fast (when I tried to check in for a Southwest flight 24h in advance to get a good seat, and the system wouldn't let me check in). Later, I dug into the time settings and noticed that NTP was off. That meant that my phone was generating OTPs based on a timestamp that was 3 minutes off, which means that my OTPs were three minutes in the future and were failing at 2FA challenges. Now that my clock is back to accurate, Authenticator is working again.
