I would suggest contacting Perrla as it is their add-in.
What you can do to start with is check if their add-in is actually installed
and enabled. In Word 2007, press the Office button followed by "Word
Options". Then go to the "Add-Ins" item. Check for the Perrla add-in and see
if it is in the active section. If not, see if using the dropdown menu at
the bottom and the "Go" button can help you enable it.
Yves