Out of the blue I can not install modules at my server. curl error 6 while downloading https://packages.drupal.org/8/packages.json: Could not resolve host

[ghost]

wodby@php.container:/var/www/html $ composer require "drupal/twig_tweak:^3.1"
./composer.json has been updated
Running composer update drupal/twig_tweak
Gathering patches for root package.
Loading composer repositories with package information

Installation failed, reverting ./composer.json and ./composer.lock to their original content.
The following exception probably indicates you are offline or have misconfigured DNS resolver(s)

In CurlDownloader.php line 377:

  curl error 6 while downloading https://packages.drupal.org/8/packages.json: Could not resolve host


require [--dev] [--dry-run] [--prefer-source] [--prefer-dist] [--prefer-install PREFER-INSTALL] [--f [--no-update] [--no-install] [--update-no-dev] [-w|--update-with-dependencies] [-W|--update-with-al] [--with-all-dependencies] [--ignore-platform-req IGNORE-PLATFORM-REQ] [--ignore-platform-reqs] [--sort-packages] [-o|--optimize-autoloader] [-a|--classmap-authoritative] [--apcu-autoloader] [--apcu-EFIX] [--] [<packages>...]

Composer works just fine at my local machine. Can somebody tell me what the problem is it?