Most instruments are not working by not giving any sound.

We don't know the exact reason of this bug which seems to occur only on the Mac version of Ardour. However, we have found a usable workaround:

Open the plugin on a MIDI track and then just save your Ardour session and then close it. After you reopened the session, all instruments of the plugin are working correctly. So the problem does only seem to occur if a new instance of the plugin is being opened the first time in a session and not being saved yet.

Since this problem only is known to occur in Ardour, we suspect that Ardour is not initializing the plugin correctly on its first launch. Feel free to bring this problem to the attention of the Ardour developers.