Hey @Filip_Fabijanic, really sorry for the trouble here my friend.
The problem here is that myBalsamiq doesn't have the updated iPhone 6/7 control, and your wireframe doesn't fit in the iPhone 5 control.
If you swap to the iPhone 5 control in Mockups 3, make adjustments to your wireframe, and then export it, it should import fine.
I'm sorry again for the hassle. Once Balsamiq Cloud is ready, this will no longer be a problem. Let me know if there is anything we can do to help!