Internal Server error on Menu Apps

Hi i have an issue with my nextcloud Installation.
I have installed nextcloud on a Qnap NAS via web installer. Everything works so far but if i click on “Apps” i see an Internal server error.

On Admin error protocols i can see one error
Exception: Call to undefined function OC\Http\Client\dns_get_record() in file ‘/share/CE_CACHEDEV1_DATA/Web/nextcloud/lib/private/Http/Client/DnsPinMiddleware.php’ line 57

On Qnap NAS i have a DNS via As said before if i enter i have access to nextcloud but cant download any apps.

How can i resolve that?