With the ip address being a 10.* address, it looks like you need to make sure you're using an On-Premises Gateway. My problem is that the screen to add the connection doesn't allow me to select a gateway!
Edit: If I create a new Dataflow, I can select Redshift as the data source, then in the next config screen I can select a gateway. I don't need to save the dataflow, the connection is created regardless.
