I have found that I manually have to download the plugins and manually add them to the /grafana/data/plugins folder. You can then either restart the docker container or use "sudo service grafana-server restart" to restart Grafana alone.
I am not sure if they are simply getting installed to the wrong folder or if it is just failing in general.
I did come here to ask if this is still being maintained. Grafana is a couple versions behind at least and I am sure that other services are behind as well. I like how this puts everything in to a single container. If this is not going to get updated, is there guide out there that will allow us to update and then make a PR?