Hi there! I’m sorry to hear that you’re facing an error while trying to pay at SONIC Drive-In. I can imagine how frustrating that must be. Let's work through this together to find a solution.

First, could you let me know if you see any specific error message when this occurs? Also, have you tried any troubleshooting steps already, like restarting the app or your iPhone?

In the meantime, here are a couple of general steps that might help resolve the payment issue:

1. Check Your Payment Method: Ensure that your payment method is valid and that there are no restrictions by your bank. Sometimes, card issues can cause errors during the checkout process.

2. Tip Setting: Some users have reported success by adjusting the tip option. You could try selecting "custom" for the tip and entering zero. Then give it a moment to load, and see if that resolves the payment issue.

3. App Updates: Make sure your SONIC app is updated to the latest version. Go to the App Store, search for SONIC Drive-In, and check for any available updates.

4. Reinstall the App: If the above steps don’t work, uninstalling and then reinstalling the app might help clear any glitches.

If the problem persists after trying these tips, please let me know, and we can look into more advanced solutions or contact support if necessary. Are you satisfied with the solutions I provided?