slow.tarmo.cz has an A (IPv4) record (90.176.149.141) 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 slow.tarmo.cz/90.176.149.141: Get "http://slow.tarmo.cz/.well-known/acme-challenge/letsdebug-test": dial tcp 90.176.149.141:80: i/o timeout
Trace:
@0ms: Making a request to http://slow.tarmo.cz/.well-known/acme-challenge/letsdebug-test (using initial IP 90.176.149.141)
@0ms: Dialing 90.176.149.141
@10000ms: Experienced error: dial tcp 90.176.149.141:80: i/o timeout
A test authorization for slow.tarmo.cz to the Let's Encrypt staging service has revealed issues that may prevent any certificate for this domain being issued.
Fetching http://slow.tarmo.cz/.well-known/acme-challenge/XZmpDVGfdjtFbtAXvwCyGwAFA76uGgd9l1bktQOKfI0: Timeout during connect (likely firewall problem)