I have been having the same problem for months since upgrading my iphone 6. Apple was NOT helpful as I spent hours on the phone with them troubleshooting doing the same things I had read online to try. None of that worked. They directed me to the apple store. I spent an hour there. They re-formatted my phone to its factory status, which I didn't want to do but was willing to try anything. They said "that fixed it" only to find out as soon as I left that they were wrong. They told me because the phone was out of warranty that I would have to pay 280 dollars to replace it.
Not only does my phone GPS not find my location which is problematic enough, but it has difficulty picking up wifi signals as well. I have to be within 5 feet of my router to get a wifi signal. This has caused huge data problems for me as well.
I feel like Apple has had plenty of time to resolve this problem if it were a software issue. I feel like when they make new phones they update the software and it screws with the old hardware, causing internal problems with apps that have been optimized for new hardware.
I have reached the point now where I am so frustrated with the whole situation and Apple not standing by their hardware/product, that I am planning on buying a Samsung phone. I realize Apple won't lose sleep losing my business, but I at least hope someone reads this and realizes how bad of a look it is for a company that has always prided themselves on their seamless customer service and convenience.