Amazon AWS appears to have resolved the issue on their side. As always, we recommend using a Yubikey or software based TOTP code for 2FA such as Google Authenticator or Duo to access your vault.

We are investigating SMS delivery issues with US Carriers (Verizon). We have opened a ticket with Amazon AWS and will post updates as soon as possible. If you need to switch to a different 2FA method, please contact support or your Keeper Administrator.