find my phone not working with ios9.2

I bought a new iphone 6s in December and I have tried everything to make it locatable when using data, not on wifi. Every other iphone I have tried from iphone 4 upwards is found easily via find my phone app. I have swapped out the sim card and also tried it in every iphone and they can be found easily.

The 6s is not.

I have looked through all the setting side by side with my iphone 6 and they are identical yet while out travelling my 6s is only found when I connect to a wifi signal.

I've been using iphones from day 1 yet I can not find a solution to this problem.

Help would be great.

D