Unable to reach DuckDNS.org!

[headcase0570]

Just installed this bit of software on a remote server, but I can't get it to work. I've set up a domain on DuckDNS, copied and pasted the domainname and token into DuckDNS Update but I keep getting this error:

I've created firewall rules to allow this software unrestricted internet access (in- and outbound) and even tried it with a fully disabled firewall, just as a test.