A test authorization for khongcotien.top to the Let's Encrypt staging service has revealed issues that may prevent any certificate for this domain being issued.
Error getting validation data
Challenge update failures for khongcotien.top in order https://acme-staging-v02.api.letsencrypt.org/acme/order/5751349/1584691688
acme: error code 400 "urn:ietf:params:acme:error:connection": Error getting validation data