Unable to import Prometheus datasource (404 Not Found)

I have a prometheus datasource I can access via web-browser with no problem: http://localmachine1:9617/metrics

I have grafana setup in a docker container in another machine. When I try to import that datasource (I tried both, server and web browser mode), it did not work.

With server mode (I think this should be the one that works), I get a 404:
Request URL: http://localmachine2:3000/api/datasources/proxy/17/api/v1/query?query=1%2B1&time=1603516350.774

Response: 404 page not found

The web UI only shows: “HTTP Error Not Found”

Not sure what I am doing wrong. I read this thread but did not work for me.

this is a connection problem, this forum can not help here, sorry.