A test authorization for aks-amt.alfing.de to the Let's Encrypt staging service has revealed issues that may prevent any certificate for this domain being issued.
2001:67c:2378:8015::156: Fetching https://www.aks-amt.alfing.de/en/page-not-found.html: received disallowed redirect status code
aks-amt.alfing.de has multiple IP addresses in its DNS records. While they appear to be accessible on the network, we have detected that they produce differing results when sent an ACME HTTP validation request. This may indicate that some of the IP addresses may unintentionally point to different servers, which would cause validation to fail.
[Address=2001:67c:2378:8015::156,Address Type=IPv6,Server=Apache/2.2.15 (CentOS),HTTP Status=301,Number of Redirects=2,Final HTTP Status=200] vs [Address=3.74.177.42,Address Type=IPv4,Server=nginx,HTTP Status=301,Number of Redirects=1,Final HTTP Status=404]