@yanakar – you say that “Appearance > Install plugin works perfectly well”, but as you can see many users have issues with that, a few topics about it were created recently. So the problem exists.

@cesaroito I got fresh WPBakery version from my account page on XTemos forum and installed it via FTP. First copied files to a folder with some name, then renamed original WPBakery folder (js_composer), then renamed folder with new version to js_composer.