AADSTS50011: The reply address does not match the reply addresses configured for the application

Can anyone tell me where to update the reply address?

I have AD synced from on-prem to Azure, then I setup a website on azurewebsites.net, then created a CNAME record from portal.mydomain.com to portal.azurewebsites.net. When I try to login using portal.mydomain.com I get:

AADSTS50011: The reply address does not match the reply addresses configured for the application.

Can anyone help? Thanks

Frank Russo