When you get
"Can not execute Sonar: You must install a plugin that supports the language XYZ"
but you have the plugin for the corresponding language installed, you need to create a new Quality profile for that language.
The profile can even be empty, as long as it exists and is assigned to that language.
Login to your Sonar instance, click on "Settings" > "Quality profiles" and "Create" on top of the heading for the language you want to use.
Now running the Sonar-Runner or the Maven-Task will succeed.