There are a number of ways to fix this problem.
1. Make sure you have a stable internet connection.
2. Make sure the game is connected to Facebook.
3. Restart your device. You may be experiencing temporary problems sending and receiving data. Restarting your device is the easiest way to fix this.
4. Open the game settings and disconnect the game from Facebook. Then restart your device and re-enter the game. Open the game settings and connect to Facebook again.

If the problem persists, try the following:
1. Open your Facebook page in a browser.
2. Go to Settings -> Apps and Websites -> Logged in with Facebook -> Active.
3. Choose the game and make sure that your Friends List is shared.
4. Restart your device and open the game.

If the game isn't listed under Active, the game's permission to access your friends list has expired. Do the following to renew it:
1. Go to Settings -> Apps and Websites -> Logged in with Facebook -> Expired.
2. Choose the game -> Renew Access.

If none of the above steps work, try deleting the game from your Facebook app list. Doing so won't affect your game progress.
1. Open your Facebook page in a browser.
2. Go to Settings -> Apps and Websites -> Logged in with Facebook -> Active.
3. Check the box next to the game and then tap Remove.
4. Restart your device.
5. Open the game and reconnect to Facebook in the game settings.

IMPORTANT: You and your friends have to grant the game permission to access your Facebook friends list to exchange lives with each other. This permission is required under the General Data Protection Regulation (GDPR). If you granted the game access to your friends list and your friends haven't, you won't see them in your in-game friends list.