Tango on iPhone 5 family can't see me on the camera me?

My hubby has Iphone5 and I have iPhone 3GS… When I'm calling my partner we can see each other via live cam… But when we call my hubys sister in America it don't work! She has iphone 4… Any idea why? We switched the cam on so did the person in America. We can see her but she can't see us but just a black screen… Why

Buy Nokia, solve problems

This sounds very odd.

Try re-installing the app.

May I suggest switching to Skype, look it up and you'll see how much better it is.