I had the same issue connecting to Agent running in Minikube. Portainer service by default uses a bridge Network where the Gateway on IP: 172.17.0.1 Minikube has its own minikube Network with the Gateway on IP: 192.168.49.1,

So I made Portainer to join minikube Network and "wuala" agent was discovered and connected to Portainer CE as another Kubernetes environment