KB: Cannot make project available online due to Unknown Server

Solution Details

This project may have previously belonged to a workspace or other managed content server.  You can use the Project Packager Wizard to clear this information. 

Accessing the Project Packager Wizard:
The Wizard is launched using one of the following methods:
  Select Project » Project Packager from the main menus.
  Right-click on a Project in the Projects panel then select Project Packager.
  Type C, P in the PCB editor workspace.
 
In the Zip File Options page, look for the Managed Projects section, where you can select the option "Unlink project from the server during packaging" - check this box if you wish to stop the synchronization between your local project and the managed incarnation of it that was made available in a workspace.  Doing so will ensure the link information to the mirrored project in the Workspace - which resides within the project file (*.PrjPcb) - is removed as part of the packaging process.
 
 
Here's more information:
Project Packager Wizard
 
Afterwards, you can expand the zipped folder to open the packaged project and make it available online.