with the release 2.361 (10-02-2017) a new “Addition” is listed in the change log:
“Removed plugin upload (to promote plugins to be added to Volumio plugin repo)”
That’s nice, but how can I install plugins that are not listed here?
Unless you are prepared to use the command line, you will have to wait until the plugin developer submits the plugin for publishing. This is a bit of a transition period, but ultimately it is aimed at improving the user experience. Have a read of this thread require-plugins-uploaded-plugins-repo-t8116.html