You've upgraded Revit and Navisworks but all your files are 2012 version or earlier. Rather than loading each file individually and having to go for a coffee break whilst you wait for them to upgrade and see the message below, there is a plug available through Autodesk Exchange which will allow you to upgrade them all at once.
You can set this running overnight and come into work the next day to your newly upgraded files, it will also maintain you file structure if you have different disciplines in different folders.
It's a free application available from the link below. You need to load any file into Revit first then you will be able to access it through the Add-Ins tab.