Hi - I’m new to this, so it may seem a silly post. I’ve just bought a UR22. I loaded the version of Cubase AI6 that cane with the UR22 and all worked fine.

I’ve now loaded Cubase Artist 7 - it works fine with midi and instrument tracks - but I’m getting no audio signal. The device setup window tells me that the two input ports on the UR22 are inactive - and I can’t find any way of making them active - help!

Did you select the ASIO driver in your VST Device settings?

Yes I did. One strange thing I’ve noticed though - if I open Cubase AI 6 - then the audio is working perfectly

Makes me wonder if perhaps CA7 is interpreting the prefs from CA6.
You are not running both versions concurrently?
If you copy your Pref files for CA6 to somewhere else temporarily see if it works.
Perhaps setting the check box for releasing the driver (CA6) might help?