Adding support assist fails

Hello,

I'm trying to add support assist to IDRAC 9 enterprise licensed server (FC640) to make tickets automatically upstream. However, registration fails during the second step (Proxy information) with error

Authorization Failed: retry network connection

However I'm not able to see anything being blocked on firewalls out from data center. Where is support assist trying to connect to? IDRAC should be allowed to send packets out from the data center without limitation at this moment.