Troubleshooting Tip: SMS gateway using HTTPS protocol unable to send a text message: HTTP request failed

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Description	This article provides the solution when getting the below error in the SMS gateway (HTTPS protocol) 'Unable to send a text message: HTTP request failed (url: https://x.x.x.x/, status: 0, res: ). Please check your configuration'.
Scope	FortiAuthenticator SMS Gateway HTTPS protocol.
Solution	Error message as below:   Packet capture shown as below: * Connection closed by FortiAuthenticator after Change Cipher Spec. Resolution: Ensure that the server CA certificate is imported into FortiAuthenticator by going to Certificate Management ->Certificate Authorities > Trusted CAs. It is possible to  manually import the CA certificate or 'Learn Certificate'.  Ensure the API URL hostname matches the server certificate common name.   Ensure FortiAuthenticator could resolve the URL hostname to an IP address.