Apologies if I was not clear: I obviously followed the prompt and quit the app several times before deciding to reply to your message. It's still giving me the same message.
Sorry about this: Very unusual. If the app can't access the library, presumably the 3+3 thumbnails on Home screen and the Top-30 report in View menu are also blank? Please reboot the Mac and try; if even that doesn't help please email us via the app mentioning your macOS version, so we can troubleshoot step by step.