Katello: unable to fetch software from a repository -> “HTTPS Error 503 - Service Unavailable”

I’m really a newbie of this product so forgive me for any trivial question.
Anyway, I have installed Foreman + Katello products on a Centos 7 and added several repositories (base-extras-katello).
After that, I tried to add a Content Host to my Foreman installation (since I would like to check software compliance and so on).
I have used the subscription-manager so I can see currently the host via Foreman UI. Unfortunately, when I try to execute yum install htop (for instance) on the client server, I receive the following error:

htop-2.2.0-3.el7.x86_64.rpm FAILED

: [Errno 14] HTTPS Error 503 - Service Unavailable

If I try

wget https://server.mydomain.com/pulp/repos/Default_Organization/Library/custom/el7_repos/epel_x86_64/Packages/h/htop-2.2.0-3.el7.x86_64.rpm

I receive:

Resolving server.mydomain.com …
Connecting to server.mydomain.com ||:443… connected.
HTTP request sent, awaiting response… No data received.

is there anyone that can give me a hand?

I saw that into foreman-ssl_error_ssl.log there was a lot of attempt and failure as below:

HTTP: attempt to connect to (*) failed

I don’t know where it is configured the use of an internal proxy, anyway I set my cntlm instance to listen on
After that, I faced a new error:

:peer did not return a certificate – No CAs known to server for verification?

So, into 05-foreman-ssl.conf I disabled the SSLVerify (to none).
With this configuration (not really correct I know) I have no error regarding SSL but on client’s side I receive a lot of timeout:

Default_Organization_el7_repos_zabbix_30_x86_64 | 2.1 kB 00:00:00
http://mirror.centos.org/centos/7/os/x86_64/repodata/repomd.xml: [Errno 12] Timeout on http://mirror.centos.org/centos/7/os/x86_64/repodata/repomd.xml: (28, ‘Connection timed out after 30002 milliseconds’)

so? what can I do?