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Similar to email, even though the vast majority of Stytch SMS and WhatsApp messages are delivered successfully, exceptions can occur. Below are some common causes of SMS and WhatsApp deliverability issues:
  • The receiving number is invalid or inactive.
  • The receiving device is currently turned off or is out of cell coverage.
  • The phone number that Stytch messages are sent from was marked as blocked on the receiving device.
  • The user’s phone carrier receives the SMS but otherwise drops or delays the message.

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Troubleshooting steps

  • User hitting invalid_phone_number errors:
    • The phone number does not match the E.164 format: [+][country code][phone number including area code]. For example, +15551234567.
    • The number matches the E.164 format but is still not a valid phone number (for example, the specified country code does not exist).
  • Successful Stytch requests where the user does not receive the SMS or WhatsApp message:
    • Check Stytch logs for the user via Event logs in the Stytch Dashboard. If there’s an issue preventing SMS or WhatsApp messages from being successfully triggered, you may see Error logs there. If you don’t see any requests for that user (neither Success nor Error logs), there may be something preventing Stytch endpoints from being called at all for the user. In that case, we recommend taking a look at your own internal application logs to pinpoint the issue. If all requests appear to be successful, there may be something preventing messages from reaching your user’s device.
    • Confirm that the user’s mobile device is powered on and within cell coverage.
    • Confirm that the user can receive SMS or WhatsApp messages from other numbers.
    • Confirm that the user is on their home carrier network. Our messaging providers cannot always guarantee message delivery to devices roaming internationally or off-network.
    • Confirm that the phone numbers used to send Stytch messages are not marked as blocked on the user’s device. If you’re not sure which phone numbers Stytch messages are sent from, please reach out to support@stytch.com for assistance.
If you’ve completed the above troubleshooting steps and are still having trouble pinpointing the issue, we can check our messaging provider’s logs and share the result with you (please reach out to support@stytch.com if interested). Note that once a message is successfully delivered to your user’s phone carrier, we no longer have visibility into why it didn’t reach their device.