It seems I have a permission problem I can't remedy.
This is Video module, which isn't working. When I realized, I see it produced a directory: /sites/default/files/videos/ This directory owner and group are set to 99/99. It even doesn't accept chown/chmod even from Cpanel, and I can't upload files there.
How did this happen, and how can I remedy this? Thank you for your continuous help!