I’ve currently unable to communicate with my A4 via USB. While the Analog Four USB connection is recognised by my PC (W8), my DAW (Live), and C6, but it refuses to either send or receive MIDI/SysEx with them.
I’m having to do everything via DIN MIDI at the moment.
I’ve tried 2x USB cables, different ports, and numerous power cycles.
It was working fine last week.
Any ideas? Needless to say, output is set to MIDI+USB, but i’ve tried USB only, and i’ve tried disconnecting the DIN MIDI cables.
Problem fixed with a USB driver uninstall and reinstall.
I should have tried that before posting, but hopefully this will help someone else who forgets to try that if they have a problem. 
sorry, which driver are you speaking about?
I don’t even know there is one to be installed…
It was just whatever one it is that windows auto installs since every device needs some form of driver.
aaah you’re on Windows…sorry !! yeah, i remember that everytime you plug somthing it starts trying to install at least something…