Can't import tracks anymore, red circle appears

Hi, 

I've previousy been able to import tracks and now, all of a sudden, I can't import any - neither by drag and drop or by importing through the 'File' function. The tracks are all mp3 files and purchased on beatport, so shouldn't be an issue with the file itself. 

When I try to import a track, it just shows me a red cirlce with a diagonal red line (like a stop sign) and nothing else happens. 

Please advise on how to fix this. 

Thanks!