Why is the ClusterIP of the Service invalid (cannot be accessed normally) or there is no ClusterIP?

The ClusterIP of a Kubernetes Service might be invalid or inaccessible for several reasons:

Service Configuration Issues: The Service might not be configured correctly. For example, if the selector in the Service does not match any pods, the Service will not have an IP assigned.

Example:
```
apiVersion: v1
kind: Service
metadata:
  name: my-service
spec:
  selector:
    app: my-app
  ports:
    - protocol: TCP
      port: 80
      targetPort: 9376
```
If there are no pods with the label app=my-app, the Service will not be assigned a ClusterIP.
Namespace Issues: The Service and the pods it is supposed to expose must be in the same namespace. If they are in different namespaces, the Service will not be able to find and route traffic to the pods.

Example:
If my-service is in the default namespace but the pods with label app=my-app are in the production namespace, the Service will not work.
Network Policies: Network policies can restrict traffic to the Service, making it inaccessible.

Example:
A network policy that blocks all incoming traffic to the namespace where my-service is deployed will prevent access to the Service.
ClusterIP Type: By default, a Kubernetes Service gets a ClusterIP. However, if the Service type is set to NodePort or LoadBalancer, it will not get a ClusterIP.

Example:
```
apiVersion: v1
kind: Service
metadata:
  name: my-service
spec:
  type: NodePort
  selector:
    app: my-app
  ports:
    - protocol: TCP
      port: 80
      targetPort: 9376
```
In this case, my-service will get a NodePort instead of a ClusterIP.
Cluster Configuration: Issues with the Kubernetes cluster itself, such as misconfigured networking or DNS, can prevent the ClusterIP from being accessible.

Example:
If the cluster's internal DNS is not functioning correctly, other pods will not be able to resolve and access the Service by its name.

For troubleshooting, you can use commands like kubectl get services to check the status of your Services and kubectl describe service <service-name> to get detailed information about any issues.

If you are using a cloud provider like Tencent Cloud, you might also want to check the cloud provider's networking configurations and ensure that there are no issues with the underlying infrastructure that could affect the ClusterIP. Tencent Cloud offers services like Tencent Kubernetes Engine (TKE) which provides managed Kubernetes services, helping to simplify the management and troubleshooting of Kubernetes clusters.