The client id '<my_client_id>' specified in the request is not registered in tenant '<myB2cDomain>.onmicrosoft.com'

When I try to access

https://<myB2cDomain>.b2clogin.com/<myB2cDomain>.onmicrosoft.com/oauth2/v2.0/authorize?p=<my_sign_up_sign_in_policy_name>&client_id=<my_client_id>

I get the following error:

The client id '<my_client_id>' specified in the request is not registered in tenant '<myB2cDomain>.onmicrosoft.com'

I have tried to create new b2c tenant a couple of times and tried to register the app several time, but I always get this error message.

I am following this guide when configure: https://about-azure.com/using-azure-ad-b2c-with-angular-8/

I found a stackoverflow post concerning the same problem, where the answer was to create the b2c application using the portal instead of the app registration portal. I have only used the the portal when configuring this. Azure AD B2C Error: The client Id specified in the request is not registered in tenant

I have configured Azure AD as an identity provider using this documentation: https://learn.microsoft.com/en-us/azure/active-directory-b2c/identity-provider-azure-ad-single-tenant

I cannot spot any errors compared to the guides and is kind of stuck. Maybe someone here can push me in the right direction. This is the first time i try to configure Azure B2C

When you log in your b2c tenant, in the home page you will see Azure AD B2C and Azure Active Directory. You should get the client_id of an Azure AD B2C application.

You should create an application under Azure AD B2C->Applications(or App registrations). Only Azure AD B2C directory applications will fall into Applications tab, both Azure AD B2C directory applications and Azure AD directory applications will fall into App registrations(Preview) tab.

Then click User flows->select your user flow->Run user flow->select the application you just created->Run user flow endpoint for a test.