Sometimes when you're switching between SIMs on an iPhone or iPad, your iMessage settings need to be reset in order to work properly.
Here's how to reset iMessage:
- Tap "Settings"
- Go to "Messages" and toggle "iMessage" OFF
- Go to "FaceTime" and toggle "FaceTime" OFF
- Restart your iPhone
- Go back to "Settings"
- Go to "Messages" and toggle "iMessage" ON
- You'll see it says "Waiting for activation"
- Tap "Send & Receive"
- Make sure your Apple ID email address is checked off
- Go to "FaceTime" and toggle "FaceTime" ON
Selecting your email address will allow you to continue to send and receive iMessages using your brand-new eSIM data connection, without relying only on your phone number.