Since I last updated to Xcode 6.1 and Yosemite, the map views in my app started to appear blank either in ios7.1 simulator or my iPhone4 (iOS7.1).
I could replicate the situation by creating a brand new single view application with just a MKMapView and although it appears correctly in iOS8 simulators, in the iOS7.1 simulators or my iPhone4 it shows only a blank screen. The iOS Deployment Target is set to iOS 7.1.
I tested this simple app in a friend's Mac with Mavericks but the same situation occurs.
Is this some bug of Xcode 6.1 or SDK, or do I have to add something to run maps on iOS7?
I faced the same problem. To fix it, you have to disable Size Classes. Go to Storyboard and in the right sidebar, you should see a check box saying 'Use Size Classes' under 'Interface builder document'. Untick it and you should see the map again.
Read this to find out why this happens: