A request to your domain revealed that the web server that responded may be the administrative interface of a modem or router. This can indicate an issue with the port forwarding setup on that modem or router. You may need to reconfigure the device to properly forward traffic to your intended webserver.
The web server that responded identified itself as "micro_httpd", which is a known webserver commonly used by modems/routers.
Requests made to the domain
Request to: cdkauffmannnextcloud.duckdns.org/206.146.67.4, Result: [Address Type=IPv4,Server=micro_httpd,HTTP Status=404], Issue:
Trace:
@0ms: Making a request to http://cdkauffmannnextcloud.duckdns.org/.well-known/acme-challenge/letsdebug-test (using initial IP 206.146.67.4)
@0ms: Dialing 206.146.67.4
@84ms: Server response: HTTP 404 Not Found
A and AAAA records found for this domain
cdkauffmannnextcloud.duckdns.org. 0 IN A 206.146.67.4
Challenge update failures for cdkauffmannnextcloud.duckdns.org in order https://acme-staging-v02.api.letsencrypt.org/acme/order/5751349/15936735
acme: error code 403 "urn:ietf:params:acme:error:unauthorized": Invalid response from http://cdkauffmannnextcloud.duckdns.org/.well-known/acme-challenge/DhTp7nUbTX4DzInR82bMlUM0v4tej-Axge_klTT5bU4: "<HTML><HEAD><TITLE>404 Not Found</TITLE></HEAD>\n<BODY BGCOLOR=\"#cc9999\"><H4>404 Not Found</H4>\nFile not found.\n<HR>\n<ADDRESS><A "
The IANA public suffix is the TLD of the Registered Domain
The TLD for cdkauffmannnextcloud.duckdns.org is: org
The current status.io status for Let's Encrypt
Operational