I don't have a problem with the location but I don't find it works that well for me. for the first week it was great then it's gone down hill despite reprogramming it. I think it's my dry hands as the weather is getting colder which effects the skin I suppose. it often says make sure finger covers entire sensor rather than does not recognise so I think it does to even find any print!
I agree. I think the sensor looks for diffraction off of the front surface of the sensor's cover glass, and if your fingers are too dry, that doesn't happen.
Regarding another post further down:
I also think it's important that you put your fingers on the sensor when programming it in pretty much the same way as you will ultimately put them on it when using the phone. If you're too deliberate when programming it, then you're locked into doing it that way every time. Of course, the programming prompts sort of force you to do it quite deliberately.
I find that for me, if my fingers are not too wet or too dry, and I get the positioning good, it's surprisingly fast and reliable. But about 30% of the time I have to move my fingertip a bit to get it to "take". Still, that seems very good considering what it's got to do and that it is trying to keep unauthorized fingerprints from activating it.
I can't complain.