It would be better if you can please re-post with a screenshot, in order to understand the phenomenon better. Images/pictures speak louder than words.
Please understand this is a public forum: While attaching a Screenshot, do not provide any personal credentials, such as IP address, Card detail, email id, apple id, IMEI number, Serial Number, Phone number, Order ID, if you are sharing a map ensure your location is not identifiable, etc.
If your iMessage says "not delivered" on every message you send, but the messages are actually being delivered, there are two possible explanations for this:
- Unstable internet connection: This can cause the messages to fail to send correctly, and the "not delivered" error message may appear. Ensure that your internet connection is stable and strong before attempting to send any messages.
- Message settings: Toggle on "Send as SMS" that will send messages even if you do not have internet connection
Lastly does the Undelivered status message remain the same? Does it not change to "Read" or "Delivered".
Turn off and restart iMessage and FaceTime
- Go to Settings > Messages and turn off iMessage.
- Go to Settings > FaceTime and turn off FaceTime.
- Restart your device: iPhone
- Turn iMessage and FaceTime back on.