Being unable to visit one of your neighbors, send Sunshine, and/or send a Helicopter help usually happens when one of you is not on the latest version of the game.

 

Here's how to update your game:

 

For Android Users:

1. Find the Google Playstore on your home screen or in your app drawer and tap it to open it. 
2. Once the Playstore loads, tap the menu button on your device and choose the My Apps option. 
3. In a few seconds, you should see a list of your apps. If there are available updates, you'll see a text that says "Update" to the right of the app's name. 
4. Tap "Update All" at the top of the screen to update your apps, or you can also update them individually by tapping the update button you see right next to the game.

For iOS Users:

1. From your Home Screen, open the App Store.
2. Access the "Updates" tab in the lower right corner.
3. Tap on the Game that needs updating.
4. Enter your Apple ID and password and select OK.