Hi there! It sounds like you're experiencing an issue with CookieRun displaying endless loading and the error code (0). Let's work through some steps to resolve this.

1. Force Stop the App: Sometimes, simply force stopping the app can clear temporary glitches. Here’s how to do it:
- Go to your device's Settings.
- Tap on Apps or Application Manager.
- Find CookieRun in the list and tap on it.
- Select Force Stop.
- After that, try reopening the app.

2. Clear App Cache: Clearing the cache can help if the app is having trouble loading.
- Go back to the App Info page for CookieRun as mentioned above.
- Look for an option called Storage, tap on it, and then select Clear Cache.
- Restart the app to see if it resolves the issue.

3. Check Internet Connection: Ensure your device is connected to a stable internet source. You might want to try switching from Wi-Fi to mobile data or vice versa to see if there's any difference.

4. Reinstall the App: If the above steps don't work, uninstalling and reinstalling the app can help:
- Long press the CookieRun app icon on your home screen or app drawer.
- Tap on Uninstall.
- Go to your app store, search for CookieRun, and reinstall it.

5. Check for Updates: Make sure both your app and the device software are updated to the latest versions. Sometimes updates can fix bugs that cause errors like (0).

If these steps don't resolve the issue, there may be a larger problem with the game's servers. You could check forums like Reddit for any ongoing discussions about this error or server status updates, as they can provide real-time support from other players facing similar issues (here's a relevant Reddit thread).

Please give these a try and let me know how it goes! Are you satisfied with the solution I provided?