da.wikihoster.de has an AAAA (IPv6) record (2001:67c:1400:2180::1) but a test request to this address over port 80 did not succeed. Your web server must have at least one working IPv4 or IPv6 address. You should either ensure that validation requests to this domain succeed over IPv6, or remove its AAAA record.
A timeout was experienced while communicating with da.wikihoster.de/2001:67c:1400:2180::1: Get "http://da.wikihoster.de/.well-known/acme-challenge/letsdebug-test": context deadline exceeded
@0ms: Making a request to http://da.wikihoster.de/.well-known/acme-challenge/letsdebug-test (using initial IP 2001:67c:1400:2180::1)
@0ms: Dialing 2001:67c:1400:2180::1
@10000ms: Experienced error: context deadline exceeded
A test authorization for da.wikihoster.de to the Let's Encrypt staging service has revealed issues that may prevent any certificate for this domain being issued.
220.127.116.11: Fetching https://da.wikihoster.de/.well-known/acme-challenge/82KB4ty4MpuLgNq1lD72JQyHi3j3kMKzPUp5QmONL1Y: Timeout during connect (likely firewall problem)