I have setup Kubernetes in CentOS with 1 master and a separate node. Added Ambassador GW and later a service with mapping. When I try to access the end service using the GW mapping it responds with no healthy upstream message.
In my case the mapping was right but the service was actually in different namespace than Ambassador. I was missing the .namespace in the service name:
So change the service from service: <service.name> toservice: <service.name>.<namespace>