Assuming the Historian has been started, what is a reason tags from the System Platform might not be seen in the System Management console?

The reason why tags from the System Platform might not be seen in the System Management console is that the objects have not been deployed. In the context of AVEVA Historian and System Platform, deploying the objects is a crucial step in transferring the designed configuration from the development environment to the runtime environment where the Historian operates. If the objects, which include tags, have not been deployed, they remain in a state where they are not actively registered or available to the Historian for data collection and logging. This ensures that only fully configured and deployed objects are recognized and utilized, so without deployment, the console will not show these tags even if the Historian itself is operational.

Other options such as configuration issues, network connection problems, or permissions might affect visibility and accessibility in different contexts, but the specific action of deployment is fundamental to making objects and their associated tags visible in the System Management console.