A validation request to this domain resulted in an HTTP request being made to a port that expects to receive HTTPS requests. This could be the result of an incorrect redirect (such as to http://example.com:443/) or it could be the result of a webserver misconfiguration, such as trying to enable SSL on a port 80 virtualhost.
@0ms: Making a request to http://app01.mueleh.ch/.well-known/acme-challenge/letsdebug-test (using initial IP 91.138.73.114)
@0ms: Dialing 91.138.73.114
@200ms: Server response: HTTP 400 Bad Request