Mobile Number verification service is not working

The text-message verification service can stop working for several reasons related to security protections and regional SMS delivery limits, not because the entire service is turned off.

Key reasons this happens:

1. Block due to unusual activity

• Microsoft continuously evaluates the trustworthiness of sign-ins and verification attempts.
• If recent activity deviates from normal patterns (many sign-in attempts, new locations, new devices, etc.), the system may temporarily block sending verification codes.
• During this block, messages such as “service currently not available” or failure to receive codes are expected behavior.

2. Too many repeated code requests

• Excessive or repetitive requests for codes to the same or alternate phone numbers/emails can trigger a temporary or even longer block.
• Continuing to retry frequently can extend or reset the block period.

3. Regional or carrier SMS issues

• In some regions, Microsoft’s SMS services can have limited functionality or temporary outages, which prevents delivery of verification codes.
• Heavy compromised traffic from a specific geographic area can also cause Microsoft to slow or block code delivery from that region for protection.

4. Unsupported phone types (VOIP)

• VOIP numbers cannot be used to receive Microsoft verification codes.
• A mobile phone number must be used instead.

5. Local phone/device issues

• Phone set to block texts from unknown numbers.
• Full SMS inbox or malfunctioning messaging app.

Recommended actions:

1. Avoid repeated attempts

• Stop requesting new codes repeatedly; this can worsen or prolong the block.

2. Try another verification method (if available)

• If the account has more than one method configured (alternate email, Microsoft Authenticator, etc.), choose a different method instead of SMS.

3. Check phone and number

• Confirm the number on the account is a mobile number, not VOIP.
• Ensure the phone is not blocking texts from unknown senders.
• Clear SMS inbox or troubleshoot the messaging app.

4. Try another network

• Switch between Wi‑Fi and mobile data, or use a different network, then try again.

5. Wait out the block

• If the issue is due to unusual activity or high request volume, waiting (up to 24 hours, and if needed up to a week without repeated attempts) can allow the block to clear automatically.

If the problem persists for a work or school (business) account and no verification method works, contact the organization’s Microsoft 365 administrator or support channel so they can assist with sign-in issues and, if necessary, adjust security methods from the admin side.

References:

• Troubleshoot Microsoft verification code issues
• Common problems with two-step verification for a work or school account