If you are using a custom authentication client id in your web application, or your web application participates in the sign in, you may find you see a message “Message: Unregistered redirect_uri”.

You may find that either:

a) you have selected “my application participates in authentication” and you did not mean this

b) your application does participate, but, you have not added the proper redirect_uri to Resources/Applications/Authentication Clients in admin.