Hi there! I understand you're having trouble starting a subscription on the Guest Manual app after your trial period ended. Let's get this sorted out together.

To better assist, could you tell me exactly what happens when you try to start the subscription? For example:
- Do you get any error messages or prompts?
- Are you trying to subscribe via the app itself or through the App Store subscription settings?
- Have you checked if your payment method linked to your Apple ID is up to date?

In the meantime, here are some steps you can try to resolve the subscription activation issue on your iPhone (iOS 18.6):

1. Check App Store Subscription Settings:
- Open the Settings app on your iPhone.
- Tap your name at the top, then tap Subscriptions.
- Look for the Guest Manual subscription. If it’s listed but inactive or expired, try restarting the subscription from there.

2. Verify Payment Method:
- In your Apple ID settings (under your name in Settings), check Payment & Shipping to make sure your payment method is valid and up to date.

3. Restart the App:
- Close the Guest Manual app completely by swiping it away in the app switcher. Then reopen it and try subscribing again.

4. Restart Your iPhone:
- Sometimes a quick restart can help refresh the system and clear minor glitches.

5. Update the App:
- Check the App Store for any available updates to Guest Manual and install them.

If after these steps you still can’t start the subscription, please let me know any details such as error messages or screen behavior, and I can guide you to advanced troubleshooting or direct you to support options.

Are you able to try these steps now?