If you're on OSS, I'd recommend trying to use a CLI tool to connect. More often than not, this has to do with proxy or SSL settings, or if you're actually connecting through a VPN or SSH bastion when you connect otherwise.
But FWIW, I've used all these methods on our Cloud-hosted (GKE) Airbyte instance. Obviously with things like VPN you often have to get creative (in our case we use routing rules in our Shared VPC to force the traffic through a GCE gateway since our client's protocol isn't supported by any of the cloud-based offerings).
If it just isn't listing any objects, make sure you have the schema listed (or remove
dbo
and it'll list all of them). And then there's always permissions. Or JDBC connection flags you may need to pass.
That's why it's always best to just test with another client before you drive yourself crazy.