srimuang.ddns.net has an A (IPv4) record (22.214.171.124) 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 srimuang.ddns.net/126.96.36.199: Get "http://srimuang.ddns.net/.well-known/acme-challenge/letsdebug-test": dial tcp 188.8.131.52:80: i/o timeout
@0ms: Making a request to http://srimuang.ddns.net/.well-known/acme-challenge/letsdebug-test (using initial IP 184.108.40.206)
@0ms: Dialing 220.127.116.11
@10001ms: Experienced error: dial tcp 18.104.22.168:80: i/o timeout
A test authorization for srimuang.ddns.net to the Let's Encrypt staging service has revealed issues that may prevent any certificate for this domain being issued.
22.214.171.124: Fetching http://srimuang.ddns.net/.well-known/acme-challenge/EFPvXfREdEGkqQxgXTo36FPZw6m6tEPcwKwXajQlh4k: Timeout during connect (likely firewall problem)