Offline Mode indicates the Cylance Smart Antivirus Agent is not able to contact your Dashboard.
The Agent must be able to reach the management console / Dashboard in order to report status and receive policy updates. If for whatever reason internet is not available, the system may display Offline Mode. The Agent will continue to function as configured even when running in Offline Mode.
Please check this Knowledge Base Article for details about what IPs and ports Cylance Smart AV uses to communicate: