@Nicktron did you have any luck with this? I’m hitting I think the same issue on both my macs, app launches but the c6 window wont display.
–edit – I found a solution to my issue at least. It’s a weird workaround. Perhaps one of the c6 devs might get some light from this, but running c6 as root by typing the following into terminal works reliably for me:
cd /Applications/C6.app/Contents/MacOS/ && sudo ./C6
SAME FOR ME!! On 10.11.4.
It worked before, but now I have to use the workaround of macropod (THANKS A LOT for the tip!).
Please Elektron, set up a new Update for the important C6 app!!