Correct a mapping project that works on iPads, but not iPhones

I have a program that allows a user walking on a hiking trail to visualise a map with trails and to use the devices GPS function to show where you are on that map. A new problem has appeared. On iPads it work well allowing the use to tell where they are, but now iPhones the blue ball showing your location no longer appears. I am surprised that the iPad is working but on the iPhone it does not. You should only apply for this project if you have access to both an iPhone and an iPad. If you have this requirement then I will send you first access to the website and then to code. and you can decide whether to complete the bid on this project. To the right person this should be a very simple project and I will pay you $100 I must be able to load the program on the server and get it to run and also have you explain to me what went wrong.