I am using the plugin Dexed with Ardour. The virtual MIDI in and outputs of the plugin are connected to a hardware MIDI interface for this channel.
Using a MIDI keyboard, I can play the plugin, and replaying the track will play the keyboard as intended.
But the plugin does not receive Sysex information (eg. send a patch) nor does sending a patch by the plugin affect the keyboard.
If Dexed is used standalone without Ardour, sending and receiving Sysex works.
So are there any settings to be made, or other ways to make Ardour transmitt any MIDI messages from and to the plugin?