The Project Offline message appears when the Render parameter is set to something that is not available in the project to render. For instance, if Render is set to Paint and there is not a Paint node in the project, you would see a Project Offline error.
Grayed out when the plug-in is first applied, Render determines which node in the Silhouette project gets rendered and is automatically enabled during project creation and set based on the project type: Roto for roto projects, Paint for paint projects and Output: Composite for composite projects.