The sandbox is not in sync with the Podfile.lock
This is a common error when running on iOS or macOS after installing new packages:
The sandbox is not in sync with the Podfile.lock. Run 'pod install' or update your CocoaPods installation
Steps to try
flutter pub get
# From the root of the project folder:
cd ios
pod install
pod update
# Or likewise if you want to fix this for macOS:
cd macos
pod install
pod update
If this still does not work, you can also try a full clean:
# From the project root:
flutter clean
cd ios
rm Podfile.lock
rm -rf Pods/
pod install
pod update
More info here:
Also see the steps in this answer to this thread: