Great to find a forum like this. And especially one that has such a positive vibe about it

I have been fortunate enough to chat to just the right guy at my local music store.
Some years back, they bought the contents of a shop that went bankrupt. Among the contents were one Noah and two Noah EX's.
They didn't have any expertise in this kind of thing and their customers are mainly buying the child's first guitar and similar, so these great machines have been collecting dust in a corner and are basically brand new! One of them has been mounted in a rack, just to try it out, and two of them still their original boxes.
The shop owner didn't want to sell them with warranty, as they are now unsupported, so we decided on a price and I took all three of his hands.
I'm hoping to sell two and keep one for myself because they seem great!
However, here comes the newbie question:
I have hooked a Noah EX up to my Mac.
The Mac is too new to run the software, so I am just sending MIDI to channel 1 and running the analog outputs into my audio interface.
I see that the Noah recieves MIDI because the MIDI LED is flashing, but no sound comes out. The same goes for the Phones output.
Volume is set to 127.
Any clues why I am not getting any sound?
While I am asking, what would you deem a fair price for these machines when they are completely unused?
Thanks for any help!

//Hedefar