HTTPS connections timedout

Hi community! I am getting a situation that raise my alarms. In short, I am getting HTTPS connections timeout (no response) when yesterday I was getting perfect connections to the same site.

• The place is: where I found information about how to harden several systems; in this case, a macOS system; to clarify, I have not made any change in the system; but it was my intention to follow the guidelines to harden the system.
• Yesterday September 24th 2025 I could browse the site with no issues at all, and even I started to prepare some automation based into the Security Guidelines.
• Today, I cannot access at all to the site.

Now some additional information:

• I can browse Internet perfectly with no issues other pages, I can search using Safari and Firefox with no issues at all.
• When I try to load the site indicated, the page never load.
  • For firefox I Uninstalled completely the application, I removed the configurations at ~/Library/Application Support/firefox and I removed the cache at ~/Library/Caches/firefox ; I downloaded the last version of the browser using a VPN and I installed, and the same situation was happening.
  • Safari was in the last version for the current date.
• The system was fresh updated to 10.15.7
• To remove any situation related to the browser, I did a request from the terminal by "curl -i -v -L https/stig******.com" the result is the below:

 curl -i -v -L "https://stigviewer.com"
* Host stigviewer.com:443 was resolved.
* IPv6: (none)
* IPv4: 54.186.104.158
*   Trying 54.186.104.158:443...
* Connected to stigviewer.com (54.186.104.158) port 443
* ALPN: curl offers h2,http/1.1
* (304) (OUT), TLS handshake, Client hello (1):
*  CAfile: /etc/ssl/cert.pem
*  CApath: none
* (304) (IN), TLS handshake, Server hello (2):
* (304) (IN), TLS handshake, Unknown (8):
* (304) (IN), TLS handshake, Certificate (11):
* (304) (IN), TLS handshake, CERT verify (15):
* (304) (IN), TLS handshake, Finished (20):
* (304) (OUT), TLS handshake, Finished (20):
* SSL connection using TLSv1.3 / AEAD-CHACHA20-POLY1305-SHA256 / [blank] / UNDEF
* ALPN: server accepted h2
* Server certificate:
*  subject: CN=stigviewer.com
*  start date: Jul  3 08:49:56 2025 GMT
*  expire date: Oct  1 08:49:55 2025 GMT
*  subjectAltName: host "stigviewer.com" matched cert's "stigviewer.com"
*  issuer: C=US; O=Let's Encrypt; CN=R10
*  SSL certificate verify ok.
* using HTTP/2
* [HTTP/2] [1] OPENED stream for https://stigviewer.com/
* [HTTP/2] [1] [:method: GET]
* [HTTP/2] [1] [:scheme: https]
* [HTTP/2] [1] [:authority: stigviewer.com]
* [HTTP/2] [1] [:path: /]
* [HTTP/2] [1] [user-agent: curl/8.7.1]
* [HTTP/2] [1] [accept: */*]
> GET / HTTP/2
> Host: stigviewer.com
> User-Agent: curl/8.7.1
> Accept: */*
> 
* Request completely sent off
* Closing connection
curl: (16) Error in the HTTP2 framing layer

In the above traces we can observe:

• The name resolution is happening: success
• The TCP connection is happening ("Connected to stigviewer.com (54.186.104.158) port 443"): success
• The TLS handshake is happening: success (because it goes on with the HTTP request)
• The HTTP request is sent: success
• As the above is happening until after the TLS handshake, I am assuming no IP block is happening.

• But, no response is got

• FTR, I tried before enable the VPN, and it was happening too (using a 4G connection, no tethered, just USB-Ethernet converter between the laptop and 4G, so from the point of view of the laptop is an Ethernet connection); It is worth to say that yesterday the same connection was working too, using the above; I comment this as indicator that trying different network alternative it was working yesterday, and today no working at all in the same scenario.

Wondering if the connections in my laptop are being intercepted. Any check to make, happy to do.

I would like to double check the chain of trust on the certificates is the expected one.

Additionally, I attached the openssl execution.

Thanks in advance for any advice and response! Let me know if further information needs to be collected.

[Edited by Moderator]