Why doesn't the location work on my friends iPhone 5 when she is in Korea? She wanted to send me a current location and it isn't working. We even tried the find friends app and this didn't work either. We made sure that all location services were on.

Why doesn't the location work on my friends iPhone 5 when she is in Korea? She wanted to send me a current location and it isn't working. We even tried the find friends app and this didn't work either. We made sure that all location services were on. She also allowed her friends to view her location, but others weren't able to see her location, and she was able to see the location of her friends. Anyone have an idea? Thanks in advance.