Hi GTR I don't use FF, so can't advise on that, but it does seem that as festie said, it is a software program, so can't look at things the same way we or a doctor would.
I read somewhere (can't remember where, but believe it was based on some actual research) that all women do not always ovulate the same every month - i.e. some months a woman might not ovulate, other (most) months she might ovulate once, some other times she might ovulate twice. This can happen without there being anything wrong with the woman's fertility at all. Maybe it was BS, but interesting anyway!
The other thing I would mention is that this month is the first time I ever had a positive on an OPK (it was the Superdrug own brand one) - even the month I conceived DD2 I got only negatives...
So basically, it all seems a bit open to interpretation, gadgets like software and OPKs aren't always 100%, and our bodies don't always co-operate. Lucky, lucky us. Why can't it all be predictable and just go how we want when we want????? (I speak from the heart here!!!)
If you've been temping and it looks like you ov'd (I get a temp drop at ov, then a sharp raise next day), then chances are you did. :)