# Unable to receive MFA authentication code when signing in

Learn what you can do if you are not receiving the authentication code required when you sign into a DAT service.

1 minute to read

There can be a few reasons why you are not receiving the authentication code

1. Phone numbers outside the United States and Canada are not supported for SMS or voice-based multi-factor authentication (MFA). For all users, regardless of location, we strongly recommend switching to app-based authentication, which is more secure and more reliable. Supported options include:
   - [Google Authenticator](https://one.support.dat.com/9-troubleshooting-2734b01a/otp-through-google-authenticator-or-similar-fc80575f)
   - [Auth0 Guardian](https://one.support.dat.com/9-troubleshooting-2734b01a/multi-factor-authentication-mfa-setup-with-auth0-guard-19b1efcc)
2. If you are using a U.S. or Canadian phone number, please check the following:
   - Verify that the phone number you entered is correct.
   - Ensure the phone number contains exactly 10 digits. Do not include the country code.
   - Confirm that your device has an active cellular signal.
   - Send a text to 328674 with the word "START" and try again.
   - Contact your mobile service provider to make sure SMS messages are not blocked and that MFA or one-time password (OTP) messages are supported.
   - Ensure you have a stable internet connection.
   - If you have requested too many codes in one day, you will be limited to seeing just one code an hour. Wait one hour and try again.