Cannot choose recovery folder

I'm using Recuva v1.53.1087 (64 bit) on Windows 10. I've run a deep scan which found a few files in excelent condition. So I click the Recover button and a pop up window appears asking to select the location folder for the recovery. However the folder tree appears empty: no folders, no drives, nothing; only a white square. I've tried running as administrator and nothing appears. Am I doing something wrong?

Thanks everybody.