A brand new data file will give you this message. If you have already registered your data file this means you are opening the wrong file (either not a PF Data file or a copy of the empty original file).
To fix:
In C://PFit, delete path.txt
Confirm you are connected to the network and that you can see PFShared/PFData.df1
Open PERFECT FIT
Message: Path is missing.
click OK.
When prompted, navigate to PFShared and open PFData.df1
This will create a new path.txt on your computer that points to the data file.