air.cs.itu.edu.tr has an A (IPv4) record (160.75.154.23) but a request to this address over port 80 did not succeed. Your web server must have at least one working IPv4 or IPv6 address.
A timeout was experienced while communicating with air.cs.itu.edu.tr/160.75.154.23: Get "http://air.cs.itu.edu.tr/.well-known/acme-challenge/letsdebug-test": context deadline exceeded
Trace:
@0ms: Making a request to http://air.cs.itu.edu.tr/.well-known/acme-challenge/letsdebug-test (using initial IP 160.75.154.23)
@0ms: Dialing 160.75.154.23
@10001ms: Experienced error: context deadline exceeded
A test authorization for air.cs.itu.edu.tr to the Let's Encrypt staging service has revealed issues that may prevent any certificate for this domain being issued.
160.75.154.23: Fetching http://air.cs.itu.edu.tr/.well-known/acme-challenge/8zmgpsoFUBIq43XhYI7A9eYbBtjWdXTiUoFZJmOdYVw: Timeout after connect (your server may be slow or overloaded)
air.cs.itu.edu.tr is currently affected by Let's Encrypt-based rate limits (https://letsencrypt.org/docs/rate-limits/). You may review certificates that have already been issued by visiting https://crt.sh/?q=%itu.edu.tr . Please note that it is not possible to ask for a rate limit to be manually cleared.
The 'Certificates per Registered Domain' limit (50 certificates per week that share the same Registered Domain: itu.edu.tr) has been exceeded. There is no way to work around this rate limit. The next non-renewal certificate for this Registered Domain should be issuable after 2022-08-05 02:05:11 +0000 UTC (16h20m0s from now).