mamadisio.gr has an AAAA (IPv6) record (2a01:7e01::f03c:92ff:fedc:e5ed) 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://mamadisio.gr/.well-known/acme-challenge/letsdebug-test": dial tcp [2a01:7e01::f03c:92ff:fedc:e5ed]:80: connect: connection refused
Trace:
@0ms: Making a request to http://mamadisio.gr/.well-known/acme-challenge/letsdebug-test (using initial IP 2a01:7e01::f03c:92ff:fedc:e5ed)
@0ms: Dialing 2a01:7e01::f03c:92ff:fedc:e5ed
@79ms: Experienced error: dial tcp [2a01:7e01::f03c:92ff:fedc:e5ed]:80: connect: connection refused