Azure AD B2C: The redirect URI provided in the request is not registered for the client id... but it actually is - azure

Question

We have the following Azure AD B2C Application (which we will call aadb2c) with the following settings
Include web app/ web API: YES
Allow Implicit Flow: YES
Reply Url:
- https://localhost:44339/
- https://productionURL.com
- https://productionURL.com/
App ID URI (which is optional): none
Native CLient: NO
This Application is what our website https://productionURL.com uses to login it's users with azure AD B2C.
However, on production we keep on getting the error:
The redirect URI 'productionURL.com' provided in the request is not registered for the client id 'aadb2c'
According to this we should add the link to out reply url.
But as you can see above, we already included https://productionURL.com in the "Reply URL" section
of the Azure AD B2C blade.
What could be causing this error to happen? How do we resolve the redirect URI request not registered error?

Answer 1

It needs to be configured in the code as well and you need to make sure that the protocols match. This can also happen if there's a mismatch with the tenant ID or the app ID.
Check the B2C callback request in Chrome DevTools > Network with "Preserve log" to see what URL is being returned. This should give you insight into the problem.
As an extra measure to ensure that the protocols are matching, you can add:
if (context.ProtocolMessage.RedirectUri.Contains("http:"))
{
context.ProtocolMessage.RedirectUri = context.ProtocolMessage.RedirectUri.Replace("http:", "https:");
}

Answer 2

After hours looking at our code and finding no traces of the url without any protocol or any trace of "http:", we now had to look at our deployment orchestrator.
Apparently in Octopus we are deploying the app with an incorrect URI: it's missing the protocol "https://"