As shared in the screenshot, you are getting this error while sending document for signature. Have you tried sending any other document than this one? Are you experiencing the same error with that too?
If yes, then you may try the same feature from DC web interface: Adobe Document Cloud and see if it lets you share the document for signature?
If you are able to send it for signature from web, then as error message says, please get in touch with your IT team and check the firewall and network settings.