Wondering if I could get some advice on how to debug this please?
A few days ago all Let's Encrypt certificates stopped renewing/issuing on one of my servers, but ZeroSSL certificates are still renewing without issues.
The error looks like a network or firewall issue so I've tested disabling the firewall but that didn't help.
And I've checked that the server can connect out to acme-v02.api.letsencrypt.org over https and that works fine.
The server is under very little and load and is fast and responsive.
I have another da server on the same network/datacenter and Let's Encrypt still works fine there.
Example of error (domain and IP redacted):
2025/12/10 11:00:16 [INFO] [xyz.com] acme: Obtaining SAN certificate
2025/12/10 11:00:17 [INFO] [xyz.com] AuthURL: https://acme-v02.api.letsencrypt.org/acme/authz/123
2025/12/10 11:00:17 [INFO] [xyz.com] acme: Could not find solver for: tls-alpn-01
2025/12/10 11:00:17 [INFO] [xyz.com] acme: use http-01 solver
2025/12/10 11:00:17 [INFO] [xyz.com] acme: Trying to solve HTTP-01
2025/12/10 11:00:33 [INFO] Deactivating auth: https://acme-v02.api.letsencrypt.org/acme/authz/123
2025/12/10 11:00:33 Could not obtain certificates:
error: one or more domains had a problem:
[opencountry.draftsite.co.nz] invalid authorization: acme: error: 400 :: urn:ietf
arams:acme:error:connection :: 123.123.123.123 Fetching https://xyz.com/.well-known/acme-challenge/xyz: Timeout after connect (your server may be slow or overloaded)
Failed to issue new certificate
A few days ago all Let's Encrypt certificates stopped renewing/issuing on one of my servers, but ZeroSSL certificates are still renewing without issues.
The error looks like a network or firewall issue so I've tested disabling the firewall but that didn't help.
And I've checked that the server can connect out to acme-v02.api.letsencrypt.org over https and that works fine.
The server is under very little and load and is fast and responsive.
I have another da server on the same network/datacenter and Let's Encrypt still works fine there.
Example of error (domain and IP redacted):
2025/12/10 11:00:16 [INFO] [xyz.com] acme: Obtaining SAN certificate
2025/12/10 11:00:17 [INFO] [xyz.com] AuthURL: https://acme-v02.api.letsencrypt.org/acme/authz/123
2025/12/10 11:00:17 [INFO] [xyz.com] acme: Could not find solver for: tls-alpn-01
2025/12/10 11:00:17 [INFO] [xyz.com] acme: use http-01 solver
2025/12/10 11:00:17 [INFO] [xyz.com] acme: Trying to solve HTTP-01
2025/12/10 11:00:33 [INFO] Deactivating auth: https://acme-v02.api.letsencrypt.org/acme/authz/123
2025/12/10 11:00:33 Could not obtain certificates:
error: one or more domains had a problem:
[opencountry.draftsite.co.nz] invalid authorization: acme: error: 400 :: urn:ietf
arams:acme:error:connection :: 123.123.123.123 Fetching https://xyz.com/.well-known/acme-challenge/xyz: Timeout after connect (your server may be slow or overloaded)Failed to issue new certificate
