[Cannot add banners in fresh install]

Hello,

I Installed Revive Server on:

"You are currently using Revive Adserver v4.1.4 running on nginx 1.10.3, PHP 7.0.33-0ubuntu0.16.04.2 and MySQL 5.7.25-0ubuntu0.16.04.2"

Everything working fine, except that I don't have ability to create new banners:
adserver/www/admin/banner-edit.php?clientid=1&campaignid=1 return ERROR 500

Tried everything - changing mysql, permissions (plus 777 to all folders), reinstall server, reading tutorials, but still....

2019/03/15 15:44:23 [error] 1004#1004: *7825977 FastCGI sent in stderr: "PHP message: PHP Fatal error:  Uncaught League\Flysystem\Exception: Impossible to create the root directory "". in /var/www/html/example.com/adserver/lib/vendor/league/flysystem/src/Adapter/Local.php:106
Stack trace:
#0 /var/www/html/example.com/adserver/lib/vendor/league/flysystem/src/Adapter/Local.php(78): League\Flysystem\Adapter\Local->ensureDirectory('')
#1 /var/www/html/example.com/adserver/var/cache/example.com_admin_container.php(97): League\Flysystem\Adapter\Local->__construct('', 0)
#2 /var/www/html/example.com/adserver/lib/vendor/symfony/dependency-injection/Container.php(335): ReviveAdserverCachedContainer->getFilesystem_Adapter_LocalService()
#3 /var/www/html/example.com/adserver/var/cache/example.com_admin_container.php(77): Symfony\Component\DependencyInjection\Container->get('filesystem.adap...')
#4 /var/www/html/example.com/adserver/lib/vendor/symfony/dependency-injection/Container.php(335): ReviveAdserverCachedContainer->getFilesystemService()
#5 /var/www/html/example.com/adserv" while reading response header from upstream, client: 78.128.126.84, server: example.com, request: "GET /adserver/www/admin/banner-edit.php?clientid=1&campaignid=1 HTTP/2.0", upstream: "fastcgi://unix:/run/php/php7.0-fpm.sock:", host: "example.com", referrer: "https://example.com/adserver/www/admin/campaign-banners.php"