Hi @David Neukam ,
Thank you for your question. I understand that users are seeing the throttling error when hitting "send a new code" and seeing the following message:
"You hit the limit on the number of text messages. Try again shortly.".
There are different MFA limits such as # of SMS per Tenant in 15 minutes, # of SMS per IP address in 15 minutes, etc. If those limits are hit, no new SMS verification code will be sent until throttling is lifted for the tenant \ IP address, etc.
Since B2C MFA relies on phone/SMS, there are also external factors that can interrupt the code delivery via SMS, like end user signal strength, carrier, network error, etc. This verification code lives for 180 seconds after requested, and if several codes are requested and failed to redeem, due to the reasons mentioned, the account can be temporarily locked.
If by chance you were testing with the same phone number multiple times in a short period of time that would cause throttling by the MFA service. (https://learn.microsoft.com/en-us/azure/azure-resource-manager/management/azure-subscription-service-limits#multi-factor-authentication-limits)
Retries aren't allowed when throttled so the users will have to restart the sign in so that the SMS verification text box is not going to be displayed.
You can also try the workaround mentioned in the Stack Overflow thread you linked, or share your HAR trace to make it easier to diagnose the precise issue.
Let me know if this helps.
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