Troubleshooting Tip: Resolving NET: ERR_CERT_AUTHORITY_INVALID Error in Google Chrome Behind a FortiGate

[Umer221]

Description	This article describes how to troubleshoot and resolve the NET: ERR_CERT_AUTHORITY_INVALID error in Google Chrome when behind a FortiGate.
Scope	FortiGate, Google Chrome.
Solution	Error: The problem occurs when a user tries to access a website via Google Chrome and encounters the error NET: ERR_CERT_AUTHORITY_INVALID. This error indicates that Chrome detects the SSL certificate is not issued by a trusted Certificate Authority. Initial Checks: Make sure SSL Inspection is enabled on the FortiGate Firewall by navigating to Policy & Objects -> Firewall Policy -> Edit Policy -> SSL/SSH Inspection. Verify if a Web Filter is applied in the same policy. Check DNS Settings: Go to the affected PC and identify the DNS settings. Note down the DNS server IP and ensure it is being used across the LAN network. Reset Google Chrome Settings: Navigate to Settings -> Advanced -> Reset settings. Select Restore settings to their original defaults. Confirm by selecting Reset settings. See screenshots of this process below:     When using deep inspection SSL/SSH profile in the FortiGate, make sure that the Fortinet_CA_SSL certificate should be listed under the list of 'Trusted Root Certificate Authority' list in the browser:  Navigate to Setting > Privacy and Security > Security > Manage certificates. Navigate to the Trusted Root Certification Authorities and import the certificate as needed: