A. 1. Restart your iPhone: A simple restart can often resolve app opening issues. Press and hold the power button until you see the 'slide to power off' option. Slide to turn off, then press the power button again to turn it back on. 2. Update the app: Go to the App Store, tap on your profile icon at the top right, and scroll down to see if GTWorld has an update available. If so, tap 'Update'.

B. 3. Reinstall the app: If the app continues to fail to open, delete it by pressing and holding the app icon until it wiggles, then tap the 'X'. Reinstall it from the App Store.