It does not work Yandex.Disk external storage

I connect to the admin panel for external storage YandexDisk (WebDAV). Gets green light:


But when I want to open a storage folder, I get an error «Storage not available»
Ubuntu 16.04, OC 9.1.2
Log file Fatal (webdav):

Exception: {"Message":"HTTP\/1.1 503 Storage not available","Exception":"Sabre\DAV\Exception\ServiceUnavailable","Code":0,"Trace":"#0 \/var\/www\/owncloud\/3rdparty\/sabre\/dav\/lib\/DAV\/Server.php(903): OCA\DAV\Connector\Sabre\ObjectTree->getNodeForPath('Yandex')\n#1 \/var\/www\/owncloud\/3rdparty\/sabre\/dav\/lib\/DAV\/CorePlugin.php(334): Sabre\DAV\Server->getPropertiesForPath('Yandex', Array, 1)\n#2 [internal function]: Sabre\DAV\CorePlugin->httpPropFind(Object(Sabre\HTTP\Request), Object(Sabre\HTTP\Response))\n#3 \/var\/www\/owncloud\/3rdparty\/sabre\/event\/lib\/EventEmitterTrait.php(105): call_user_func_array(Array, Array)\n#4 \/var\/www\/owncloud\/3rdparty\/sabre\/dav\/lib\/DAV\/Server.php(459): Sabre\Event\EventEmitter->emit('method:PROPFIND', Array)\n#5 \/var\/www\/owncloud\/3rdparty\/sabre\/dav\/lib\/DAV\/Server.php(248): Sabre\DAV\Server->invokeMethod(Object(Sabre\HTTP\Request), Object(Sabre\HTTP\Response))\n#6 \/var\/www\/owncloud\/apps\/dav\/appinfo\/v1\/webdav.php(56): Sabre\DAV\Server->exec()\n#7 \/var\/www\/owncloud\/remote.php(164): require_once('\/var\/www\/ownclo...')\n#8 {main}","File":"\/var\/www\/owncloud\/apps\/dav\/lib\/Connector\/Sabre\/ObjectTree.php","Line":159,"User":"admin"}

Do you have other Webdav resources to test? Because not all webdav-storage provide all necessary features. You can as well test yandex-webdav with the litmus test: