Hi & welcome,
As @rsx wrote maybe SELinux causing a problem. If you try this command
sestatus
You will see if enabled or disabled.
If enabled and you try this command in one bash
tail -f /var/log/audit/audit.log | grep -i denied
and trigger the check in another bash or web you’ll should immediately if SELinux blocks something.
If you didn’t enabled SELinux you have to go deeper. Because we havent’ installed check_uptime for CentOS, you could pls tell us which check this is? I only found in our ITL only the version for Windows.