Fallout Critter Pro Issue. Cannot Identify File

Hi there. I would just like to seek for some help with Fallout Critter Pro.
I was trying to open some dot pro files, but it gives me an error message saying that this file is not a Fallout Critter Pro file. (Screenshot below) How come it said that? It is clear that the file is a .pro file.
Why is there an error?
I wish I could find the fault so that I could continue editing my file.

