When deploying the 3CX inspector, it can fail with a message pointing toward a missing or invalid certification.
Steps to Remediate
Validate that the URL being inspected has a valid certificate. To do this, navigate to https://www.sslshopper.com/ssl-checker.html and add the 3CX URL to confirm.
Once you enter the site and check SSL you will be able to see if the site has a valid certificate.
The certificate must be signed by a trusted certification authority, otherwise, you may not be able to use a self signed certificate on an internal host.