| Cause | Check | Fix |
|---|---|---|
| DNS points elsewhere | dig +short domain shows another address | Fix the A record, wait for DNS |
| An AAAA (IPv6) record points elsewhere | dig +short AAAA domain | Remove it or point it to the server's IPv6 |
| Cloudflare in Flexible mode or blocking | Cloudflare SSL/TLS setting | Full (strict), and no WAF rule blocking /.well-known/acme-challenge/ |
| Too many attempts | Let's Encrypt limits retries per domain | Wait an hour and try again |
| CAA record | A CAA record that does not allow letsencrypt.org | Add 0 issue "letsencrypt.org" |
Once fixed, Domains & SSL, Add new domains to the certificate.
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