Use letsencrypt got this error.

[akong77]

Hello,
I want use letsencrypt to generate my web ssl key.I make sure dns setup done and can resolve domain.But when I click generate key will got error message.

[Thu Dec 10 08:55:30 CST 2020] _post_url='https://acme-v02.api.letsencrypt.org/acme/chall-v3/9193634542/k7kq1Q'
[Thu Dec 10 08:55:30 CST 2020] _CURL='curl --silent --dump-header /var/etc/acme-client/home/http.header  -L '
[Thu Dec 10 08:55:31 CST 2020] _ret='0'
[Thu Dec 10 08:55:31 CST 2020] code='200'
[Thu Dec 10 08:55:31 CST 2020] domain:Verify error:DNS problem: SERVFAIL looking up A for domain - the domain's nameservers may be malfunctioning
[Thu Dec 10 08:55:31 CST 2020] pid
[Thu Dec 10 08:55:31 CST 2020] No need to restore nginx, skip.
[Thu Dec 10 08:55:31 CST 2020] _clearupdns
[Thu Dec 10 08:55:31 CST 2020] dns_entries
[Thu Dec 10 08:55:31 CST 2020] skip dns.
[Thu Dec 10 08:55:31 CST 2020] _on_issue_err
[Thu Dec 10 08:55:31 CST 2020] Please check log file for more details: /var/log/acme.sh.log
[Thu Dec 10 08:55:31 CST 2020] url='https://acme-v02.api.letsencrypt.org/acme/chall-v3/9193634542/k7kq1Q'
[Thu Dec 10 08:55:31 CST 2020] payload='{}'
[Thu Dec 10 08:55:31 CST 2020] POST
[Thu Dec 10 08:55:31 CST 2020] _post_url='https://acme-v02.api.letsencrypt.org/acme/chall-v3/9193634542/k7kq1Q'
[Thu Dec 10 08:55:31 CST 2020] _CURL='curl --silent --dump-header /var/etc/acme-client/home/http.header  -L '
[Thu Dec 10 08:55:32 CST 2020] _ret='0'
[Thu Dec 10 08:55:32 CST 2020] code='400'

What's this problem?