Cubase 8.5 pro won't recognise UR22 sound card

Hello…I’ve been recording a lot of individual tracks fine recently with my Steinberg UR22 sound card & now suddenly it gives an “unmapped” message when i try to load previously recorded tracks & dosn’t seem to recognise the sound card any more…It only gives me the generic speaker one that’s with the computer…The sound card is recognised by the computer fine so its got to be a problem with cubase
Have you any ideas how i can fix this please ?