I agree it needs to be a fips enabled fortios to enable fips.
And that is my frustration
http://docs.fortinet.com/...rtigate-cli-ref-54.pdf page 508 describes the cli for it
basically the manual for my version of the software gives very clear instructions of what i need to do. If I could find a document that says except for these versions or these models then I would let it go. But all I can find is instructions on how to do this.
and yes the link is for 4.5.1 and on one unit I did down grade to 4.5.1 just to see if it worked.