Cubase Artist 7 Input Malfunctioning

I’ve just started using Cubase Artist 7 with a UR22 interface and am watching the tutorials to work out how to use it. Trying to use the Guitar & Vocal recording, but only the Guitar track works. The Vocal input keeps cutting out, and I can’t work out why. Anyone have any idea what the problem is likely to be? It seems to be the software because it happens whether I use INPUT 1 or INPUT 2 on the UR22 for the Vocal track.

Have you tried a different cable or mic?

The same cable and mic works perfectly well on the Guitar track (whether it’s plugged into INPUT 1 or 2), so I’m assuming the problem has something to do with the settings for the Vocal track.