Cant start DuckDNS add-on on Ubuntu

I’ve migrated from a working setup on a RPI3 with to a new PC with ubuntu server 18.4 + docker + Everything i’ve restored works except DuckDNS/LetsEncrypt.
Whenever i start the add-on it stops after a few seconds. its log shows:

INFO: Using main config file /data/workdir/config,

ERROR: Problem connecting to server (get for; curl returned with 6),

i can resolve domain names fine from the main machine, and can curl that adress without any problem, so the issue must be docker network related.

Anyone encountered this issue? uninstalling the add-on and rebooting havent helped.