Hi Leo,
After Windows and Opus reinstallation I do not see PDFs in the Viewer anymore. How can I fix this and see them again? See the screenshot attached:
With Regards,
Lily
Is your PDF viewer working in File Explorer's viewer panel, or is the problem in both programs?
Try reinstalling the viewer.
Failing that, if it isn't working in both Opus and Explorer, please ask the maker of the viewer for advice. It looks like PDF-XChange, based on the file types in the screenshot.
Reinstalling has helped. Thank you, Leo!