First, do not panic. Rest assured that if something is seriously wrong at the WAF side, our system engineers are most likely already working on it. More often than not, the problem is on your side and can be easily fixed. Unless multiple users or some automatic uptime monitoring tool are reporting the site to be down, chances are the site is still up and simply appears to be down for you only. A free service such as https://downforeveryoneorjustme.com/ will tell you if the site is down for everyone.
If the site is down for you only, you have probably locked yourself out. Please see "I locked myself out".
If the site really is down, you should first check with your system administrator that your server is fully operational.