One contact / recipient not receiving messages (iMessage / SMS). Unable to send messages to One Contact
If you have enabled iMessages and sending a message to another iPhone user then it will be always sent as iMessage. The same will be sent as SMS only if...
- You have no internet either over WiFi or Cellular
- The recipient has not activated iMessage.
Types of messages?
- iMessage? --> Check your internet stability and connectivity. If the Apple server is the issue, it will show here --> Support - System Status - Apple
- SMS/MMS? --> Does not need internet but contact your Carrier Service Provider for network coverage and outages ->: Down Detector - outages
Please check if contact / recipient is sending their messages from Apple ID or Phone number?
The contact / recipient will not receive messages if they have not enabled iMessage for their Phone number and also may not receive SMS if they have not enabled SMS plan for their SIM/eSIM through their carrier.
In that case they can send and receive iMessage through their Apple ID but you cannot send a text message to their phone number.
They also cannot send you an SMS from their phone number.
Try sending an iMessage to their Apple ID.