If PPM was unexpectedly halted during operation (for example, the system on which PPM is running fails), you may need to re-enable the Plug-in for PPM from Microsoft Project in order to display the PPM menu.
To re-enable the Plug-in for PPM from Microsoft Project:
Click Help > About.
Click Disabled Items.
If the Plug-in for PPM is listed, remove it from the list to enable it.