Background Information
You cannot directly save an alternate version of a project as the Published version by opening the alternate version and clicking File > Save As. The system prevents you from doing so with an error dialog. The only way to perform this action is to use an indirect approach.
Resolution
The project manager of the enterprise project in question should complete the following steps:
1. Launch Microsoft Project Professional and log into Project Server
2. Click File > Open
3. Select the version of the project you wish to save as the .Published version, and then click the Open button
4. Click File > Save As and then click the Save as File button
5. Save the alternate version of your project as an .mpp file
6. Ask your Project Server administrator to delete all Versions of the project in question from the Project Server database using the steps detailed in first half of the following FAQ:
Delete a Project Without Deleting Its Subweb
7. Import your .mpp file into the Project Server database (and connect the project to the previous project’s SharePoint subweb) using the directions in the second half of the preceding FAQ
To create an alternate Version in Project Server, refer to the following FAQ:
Create Alternate Project Versions