Let's Debug

Test result for mail.kentekenflirten.nl using http-01

mail.kentekenflirten.nl has an AAAA (IPv6) record (2a0d:7c40:3000:ac9::2) 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.
Get "http://mail.kentekenflirten.nl/.well-known/acme-challenge/letsdebug-test": dial tcp [2a0d:7c40:3000:ac9::2]:80: connect: connection refused

Trace:
@0ms: Making a request to http://mail.kentekenflirten.nl/.well-known/acme-challenge/letsdebug-test (using initial IP 2a0d:7c40:3000:ac9::2)
@0ms: Dialing 2a0d:7c40:3000:ac9::2
@75ms: Experienced error: dial tcp [2a0d:7c40:3000:ac9::2]:80: connect: connection refused
A test authorization for mail.kentekenflirten.nl to the Let's Encrypt staging service has revealed issues that may prevent any certificate for this domain being issued.
23.238.42.75: Fetching https://mail.kentekenflirten.nl/.well-known/acme-challenge/IBEfjTFn03s3uG5bc5yzXyy5dUENnKT-6GS7gIsnkWQ: Timeout during connect (likely firewall problem)

Submitted Nov 13 23:37:22 2023. Sat in queue for 5ms. Completed in 21s. Show verbose information.