Hello @C H ,
Thanks for reaching out.
Could you please examine the requiredResourceAccess (rRA) in the Application Manifest to find the corresponding permissions that have been assigned. Usually, you get this error when added something unsupported in requiredResourceAccess (rRA) field.
To know more about, refer what is requiredResourceAccess attribute.
Here is another similar thread for your reference: https://stackoverflow.com/questions/65400251/azure-b2c-app-registration-why-cant-i-change-my-redirect-uri
Hope this helps.
-----
Please "Accept the answer" if the information helped you. This will help us and others in the community as well.