Hi there! I understand you're having trouble opening the Tangled Snakes app on your iPhone running iOS 15.8.3. Let's try to get you back to playing as soon as possible.

To start, could you tell me if the app shows any error messages or simply fails to open? Also, have you tried anything so far to fix the issue?

Meanwhile, here’s a step-by-step approach to troubleshoot the app not opening:

1. Force Close the App: Sometimes the app could be stuck. Swipe up from the bottom (or double-click the Home button if your iPhone has one), find Tangled Snakes in the app switcher, and swipe it away to close it. Then try opening it again.

2. Check Internet Connection: Even if the game usually works offline, some features or the startup may require internet. Make sure your Wi-Fi or cellular data is active and stable.

3. Restart Your iPhone: Holding down the power button and sliding to power off can clear temporary glitches. After a full restart, try opening the app again.

4. Update the App: Check the App Store for any updates to Tangled Snakes. Running an outdated version might cause issues on some OS versions.

5. Reinstall the App: If none of the above work, try deleting Tangled Snakes and reinstalling it fresh from the App Store. This can clear corrupted app data.

6. Check Storage Space: Low free space can cause apps to behave unexpectedly. Go to Settings > General > iPhone Storage to see if you have ample storage.

If you’ve already tried some of these steps, let me know which ones, and I can suggest more advanced options. Also, if there is an error code or specific message, sharing it will help diagnose better.

Are you comfortable trying these now? I’ll be here to guide you through any step.