Hi there! Thanks for reaching out. I understand you're able to connect to your YI IoT cameras over WiFi but not when using your mobile data. Let's figure this out together.

First, a couple of quick questions:
1. Are you using an iPhone with iOS 18.5, correct?
2. When you try to connect over mobile data, does the YI IoT app give you any error messages or does it just fail to load?
3. Have you checked if the mobile data is working fine with other apps on your phone?

Meanwhile, here are some initial steps you can try to get us started:

1. Check Mobile Data Settings for the YI IoT app:
- Go to your iPhone's Settings > Mobile Data (or Cellular).
- Scroll down to your YI IoT app and make sure Mobile Data access is enabled.

2. Verify Camera Cloud Access:
Some cameras require cloud access to work remotely. If your mobile carrier restricts certain traffic types, this might affect connectivity.

3. Enable VPN or Disable it (if applicable):
If you’re using a VPN on your phone, try disabling it temporarily to see if that helps. Conversely, if you’re not using one, sometimes enabling a VPN can bypass carrier restrictions.

4. Reset Network Settings (only if previous steps don’t work):
Go to Settings > General > Transfer or Reset iPhone > Reset > Reset Network Settings. Note that this will clear saved WiFi passwords and VPN settings.

Let's start with these and see how it goes. Could you please try these and let me know what happens? Also, if any error messages appear, sharing those would help a lot.