failed to req API:/nacos/v1/ns/instance after all servers([localhost:8848]) tried: java.net.ConnectException: Connection refused: connect

This error message indicates that the client failed to connect to the Nacos server API endpoint on localhost:8848. The most likely cause is that the Nacos server is not running or is not accessible from the client machine.

To resolve this issue, ensure that the Nacos server is running and that the API endpoint is accessible from the client machine. You can also check the server logs for any errors or issues that may be preventing the client from connecting. Additionally, ensure that the client is configured to use the correct API endpoint and that any necessary authentication credentials are provided.