vault.burstein.de has an A (IPv4) record (92.39.23.246) but a request to this address over port 80 did not succeed. Your web server must have at least one working IPv4 or IPv6 address.
A timeout was experienced while communicating with vault.burstein.de/92.39.23.246: Get "http://vault.burstein.de/.well-known/acme-challenge/letsdebug-test": context deadline exceeded
Trace:
@0ms: Making a request to http://vault.burstein.de/.well-known/acme-challenge/letsdebug-test (using initial IP 92.39.23.246)
@9ms: Dialing 92.39.23.246
@10000ms: Experienced error: context deadline exceeded
A test authorization for vault.burstein.de to the Let's Encrypt staging service has revealed issues that may prevent any certificate for this domain being issued.
Fetching http://vault.burstein.de/.well-known/acme-challenge/2vavQ2daVJ5seXKJ2uAY2khp-UD6ifn8RtC-upx158s: Timeout during connect (likely firewall problem)