Joomla\CMS\Filesystem\Folder::files: Path is not a folder. Path: [ROOT]/images/flickr/red_carpet

There was a problem rendering your image gallery. Please make sure that the folder you are using in the Simple Image Gallery plugin tags exists and contains valid image files. The plugin could not locate the folder:

[SIGPLUS_EXCEPTION_SOURCE] Image source is expected to be a full URL or a path relative to the image base folder specified in the back-end but flickr/red_carpet is neither a URL nor a relative path to an existing file or folder.