Your website could be down for many reasons. If you have performed the typical network connectivity checks, then the issue could be that your website it subject to a malware attack. If your are comfortable with editing html code, proceed with the following:
- Log-in to your cPanel account
- Access File Manager
- The malware will likely be located in a 'php' file such as 'wp-blog-header.php' (or other similar php files).
- Look for malicious code or any anomalies in the original code code and remove.
If you require help with identifying and removing malicious code, open a new support ticket.