You cannot locate the Project Browser in the user interface.
Issue: The Project Browser may not be selected for display or may be hidden.
Windows panel
User Interface drop-down
Project Browser.
Display, and make sure that the zoom is set to 100%. If none of the above methods resolves the issue, go to forums.autodesk.com, and select Revit from the Browse by product drop-down. From here you can search the forums for more information.