Logic not letting me select an input device for external instrument

I'm trying to connect an external synthesizer that I have installed on my Macbook to Logic, and while sound comes out of the synthesizer just fine, I cannot get it to output in Logic. The synth doesn't have a way of recording audio, before you ask, so this is my only option. I think I've got the problem, that being that the input device is currently selected as "none", but whenever I try and change it, it doesn't let me, and switches back to "none".

Does anyone know why it's doing this?