Cannot access FortiGate Web GUI (web admin interface)

If the certificate on your LAN (SSH enabled) port is expired or failed to renew, the web interface simply stops working. The solution is to set the admin server certificate to use the FortiGate Factory certificate.

SSH into FortiGate and then issue the following command:

config system global

set admin-server-cert Fortinet_Factory

end

NOTE: To be sure this is your actual problem, you can turn debug on and check

diagnose debug application httpds -1
diagnose debug enable

Expect to see output from debug which looks like below when attempting to access the web interface
Can’t open certificate file …

What is FortiGate Firewall?

FortiGate is a next-generation firewall (NGFW) developed by Fortinet, designed to protect networks from a wide variety of threats while maintaining high performance. It provides comprehensive security features, including:

1. Firewall: Blocks unauthorized access to or from private networks using stateful packet inspection, allowing or denying traffic based on predetermined security rules.
2. Intrusion Prevention System (IPS): Detects and blocks attacks targeting vulnerabilities in networks and applications.
3. Antivirus/Antimalware: Scans and prevents viruses, malware, and other malicious software from entering the network.
4. Web Filtering: Controls and monitors access to web content, blocking access to harmful websites or categories like gambling, phishing, and adult content.
5. Virtual Private Network (VPN): Provides secure remote access to the corporate network via encrypted tunnels.
6. Application Control: Allows administrators to control and monitor specific applications being used in the network, restricting or prioritizing them.
7. Sandboxing: Uses a cloud-based or local sandbox to analyze suspicious files in a secure, isolated environment before they can affect the network.
8. SSL/TLS Inspection: Inspects encrypted traffic to detect hidden threats.
9. Advanced Threat Protection (ATP): Combines multiple security features, such as malware analysis and behaviour analysis, to detect advanced and emerging threats.
10. Unified Threat Management (UTM): Provides a combination of firewall, antivirus, intrusion detection, content filtering, and more in a single solution.