Azure B2C Identity Provider - is it possible to usie a Power Automate flow as a API Connector?

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Posted on by Motor-Ola

Hi community,

I have set up a power automate flow with a "when a http request is received" trigger. I added this URL to the API Connector on the azure b2c Signup/Signin user flow... calling the endpoint using a tool like Postman seems to work fine and dandy, but addeing the API Connector to the "BEfore creating the user" step only result in a "undefined" message on top of the signup form.

Any tips on how to debug this? Som kind of error log or something... or if anyone knows the API Connector only works with Azure FUnctions?

It is no trace of a request in the Flows run log. But in the Azure B2C audit log, I find this:

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Fubar 8,346 Super User 2025 Season 2 on at

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401 is unauthorized access error. Default for HTTP Request is that it is open to the world (i.e. you can call it from anywhere) - but it can be locked down with Azure API Management so if this has been setup it could be the problem.

Make sure that the call being made matches the GET/POST setting on the HTTP Request node. There is also a Setting on the HTTP Request node that allows you to reject calls that do not match a criteria you specify (but this would normally return an OK not 401 - this setting is the only other one I am aware of that will not give you a run History.

If you have it set as GET, try pasting the URL into your browser and see what response you get. If set to POST try changing it to GET (and pasting it in your browser) or creating a local web page with a Form submit of POST and call it from your desktop rather than Postman.

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Motor-Ola 14 on at

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Thanks for the reply. I'm starting to think that this is not possible using a Power Automate Flow (since the http endpoint is open and not protected in any way). I have set the trigger to post, and when testing from Postman I get a proper response with the expected json payload (which is this, just for testing):

{
    "version": "1.0.0",
    "action": "ShowBlockPage",
    "userMessage": "There was a problem with your request. You are not able to sign up at this time."
}

According to the documentation, this is supposed to make the Azure AD B2C login sequence show a page telling the user there was a problem with the signup.

So, where does the 401 come from, I wonder?

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jimothy 2 on at

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I'm trying to do the exact same thing, and I've been getting the exact same error. Have you found a solution to this yet?

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Motor-Ola 14 on at

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Hi,
I ended up creating the wanted functionality in an Azure Function. Coded in C# using Visual Code and a plugin to deploy the Function "App" onto my Azure tenant. Inside the code I used the Service Client API to do the requests to my Dataverse environment. Everything protected behind an app registration (clinet id and secret).

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CU09091118-0 5 on at

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I am also facing the same issue. Although the flow is working fine from Postman, the B2C API connector is not able to call the flow.

I have also tried creating a Logic App in Azure, but the result is same.

Only Azure Function is working.

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salesmaster 4 on at

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Using Power automate flow as a API connector in B2C will not work, since B2C API connector tries to use the different authentication mechanism (basic/certificate), but flow uses the SAS token for authentication (the sig parameter in the URL).

You can try by calling flow in Postman and add the Basic authentication. You will get the same error.

This also applies to login app.

The only option as of now is to use custom API or use flow behind a Azure APIM (I haven't tried it).

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