Hey SusanM1951,
As the issue is limited to that contact specifically, it's possible the problem is with their device or cellular service.
That said, we'd recommend reviewing this article as it provides steps to help resolve issues sending messages: If you can't send or receive messages on your iPhone or iPad - Apple Support
"If you see a green message bubble
If you see a green message bubble instead of a blue one, then that message was sent using MMS/SMS instead of iMessage. There are several reasons for this:
- The person that you sent the message to doesn't have an Apple device.
- iMessage is turned off on your device or on your recipient’s device. To check if iMessage is turned on for your device, go to Settings > Messages > iMessage.
- iMessage is temporarily unavailable on your device or on your recipient’s device.
- You might need to update your settings for Messages after you set up a new device.
Learn the difference between iMessage and MMS/SMS messages"
"If you have issues with a group message
If you’re in a group message and stop receiving messages, check to see if you left the conversation. Open Messages and tap the group message. If you see a message that says you left the conversation, then either you left the conversation or you were removed from the group message. You can rejoin a group message only if someone in the group adds you.
To start a new group message:
- Open Messages and tap the Compose button
. - Enter the phone numbers or email addresses of your contacts.
- Type your message, then tap the Send button
.
If you have other issues with a group message, you might need to delete the conversation and start a new one. To delete a group message:
- Open Messages and find the conversation that you want to delete.
- Swipe left over the conversation.
- Tap Delete.
In iOS 16, iPadOS 16.1, and later, you can recover a message if you deleted it within the last 30 to 40 days."
Thanks!
