I had the same problem on my last 2 flights. It worked OK for the 1st hour, then stopped. I talked to Foreflight and they
said that it was a problem with their latest upgrade 4.7.1. Here was their temporary fix until the next upgrade.
1. Exit Foreflight and go to the main Ipad home screen.
2. Press the button at the bottom of the Ipad twice in a row. A list of the last apps you've used should slide up at the
bottom of the screen, and the top part of the screen will go dark.
3. Find the Foreflight icon on that list. Tap and hold the icon until it starts to wiggle, then tap the - sign in the top left corner
of the icon. This will stop Foreflight from running in the background.
4. Tap on the top of the screen or click the button at the bottom of the Ipad to exit.
5. Tap the Foreflight icon to re-open the app.
Hope it helps.
Dave