Registration SUSE over proxy

I’m trying to register SUSE for SAP on AWS EC2. All internet traffic must go through proxy. Originally I used SUSEConnect which registers with Now I need to use registercloudguest (as described here) which uses for the registration process. I think the fact that does not have a public DNS record is the cause of my problem because I get “503 Service Unavailable” from the proxy. Any ideas on what can be done in this case? Thank you.