How to add a datasource to grafana pulgin?

I am trying to connect the Grafana plugin to a data bucket using InfluxDB.
I follow the documentation on Grafana Plugin and I get error message when pushing “Save & Test”.

Assuming that I use " " to access to my private instance.

If I use “” or “” or “” as the URL, the error message is “Network Error: Bad Gateway(502)”.
If I replace the URL by “”, the error message becomes “Network Error: Not Found(404)”.
Finally, if I use “” or “”, the error message becomes “InfluxDB Error: error authorizing query: create admin user first or disable authentication” even though my auth are all disabled as the picture shown in the Grafana Plugin.

May I ask what the URL should be and if there is anything I need to set up before using this plugin?
I just developed the private instance today and it only contains one device, one dashboard and one empty data bucket.

Thanks in advance.