Forwarding to sipgate not working

Hi I’m desperately trying to forward our flynumber to a service called sipgate. Haven’t found any topics here so I thought if anyone might have an idea. (this is a standard cloud based pbx using standard sip protocols)
I tried all sorts of configs but I either get a “Decline” or “Proxy Authentication Required”… any suggestions?


This looks to be a restriction on their side, can you ask them if your SIP URI is open to outside DID providers?