New iMessage texts not appearing in chat thread

If You Are Not Receiving iMessages from One Particular Person

If you are able to receive iMessages from everyone else but iMessages from one specific person are not reaching you, first check whether that person has your correct phone number saved and is sending the message to the number currently associated with your iPhone.

They may have:

• Saved an old or incorrect phone number in their Contacts.
• Accidentally selected the wrong number from your contact card.
• Continued using a number you no longer use with iMessage.
• Started a conversation using an old iMessage thread that is associated with a different number or email address.

Ask the person to check your contact details and verify the exact phone number they are sending the iMessage to. They should also try starting a new Messages conversation by manually entering your current phone number rather than replying to an old conversation.

On your iPhone, you can verify which numbers and email addresses are enabled for iMessage under:

Settings → Apps → Messages → Send & Receive

Make sure your current phone number is listed and selected under “You Can Receive iMessages To and Reply From.”

This is an important check when the problem occurs with only one person. If everyone else can send you iMessages successfully, the issue may be with that person's saved contact information or the address they are using to send the message, rather than with your iPhone or iMessage itself.