Downloading apps error with fresh nextcloudpi install


Nextcloud version (eg, 12.0.2):
Operating system and version (eg, Ubuntu 17.04): raspberry pi 3 with nextcloudpi
Apache or nginx version (eg, Apache 2.4.25):
PHP version (eg, 7.1):7.2.9

When i try to download new apps or even when i try to update the calendar extension i got this error message:

GuzzleHttp\Exception\ConnectException: cURL error 6: Could not resolve host: (see

Any help will be appreciated