Hi @xp_xm
checking your domain via https://check-your-website.server-daten.de/?q=sig4pg.com - you see:
Your name servers are terrible buggy.
A lot of error messages:
X Fatal error: Nameserver doesn't support echo capitalization. That's critical if you want to create Letsencrypt certificates. Read draft-vixie-dnsext-dns0x20-00 (2008). If a dns client asks "ExAmPlE.cOm", the name server must answer with the same name, not with "example.com". Creating Letsencrypt certificates isn't possible. Your name server provider must update the software.: ns1.huaweicloud-dns.cn / 122.112.208.53
These huaweicloud servers are known as buggy.
Your error message says: The primary servers of Letsencrypt are able to check your dns. But the secondary are not, so the validation fails.
--> switch to another dns provider or ask there.
PS: You are not the first user with these problems. See