Failed to load external entity

Hi,

we use this PHP Script to include an extension

	libxml_use_internal_errors(true);
	$sxe = simplexml_load_file('https://www.domain.com/path-to-file/filename.xml');
	if ($sxe === false) {
		echo "Laden des XML fehlgeschlagen\n";
		foreach(libxml_get_errors() as $error) {
			echo "\t", $error->message;
		}
	}

and get this error “failed to load external entity”.

When we deactivate your plugin everything works fine.
What have we to change to get this solved?

Best Regards
Marc