Two questions here:
First, for your problem, it sounds like the setup is OK. Perhaps something in the settings?

Second question (for me!), how do you setup the A4 usb midi in ableton? I have yet to do this, I just sync via midi. By setup, I mean, what do you turn “on” and do you pull it from a list of devices or anything? Maybe you can take a screenshot of the ableton setup panel?