iMessage, "Not registered"

[Jasper7]

When using iMessage on my iMac I get a message indicating that a message for one of my contacts (and only one) cannot be sent because it isn't registered with iMessage. I've searched for help on the Internet but have found nothing satisfactory; in fact some of the instructions don't even appear to match either my phone or iMessage on the computer. I can send messages to that number from my phone, however. I' running mojave on the computer.

 

[Cory Cooper]

Hello,

When you send a text from your iPhone to that number, are the text bubbles green or blue? If they are green, that means they are being send as standard SMS text messages, and not to an iCloud/iPhone using Apple's iMessage protocol, which has blue text bubbles. You can still send text messages to that number from your Mac, if your settings on the Mac and the iPhone are correct for the Messages app, similar to this:

Mac > Messages > Preferences > Accounts
You can be reached for messages at (all checked):
-Your iPhone number
-Your iCloud email account

Start new conversations from:
Your iPhone number


iPhone > Settings > Messages
iMessage enabled

Send & Receive > 2 Addresses (or whatever number it shows)
YOU CAN RECEIVE IMESSAGES TO AND REPLY FROM (all checked)

START NEW CONVERSATIONS FROM
Your iPhone number (checked)
iCloud email address(es) (not checked)

Does the contact with that phone number have an iPhone and are they using an iCloud account?

C

 

[Jasper7]

"Does the contact with that phone number have an iPhone and are they using an iCloud account?"

No. I have previously been able to send and receive from my Mac to and from that number. It suddenly refused to work.

The text bubbles to that number are green.

Mac>Messages>Preferences> Accounts all checked.

iPhone>Settings>Messages: iMessage enabled. Send & Receive has my phone number. Pressing on Send & Receive for next page: 'YOU CAN RECEIVE IMESSAGES TO AND REPLY FROM" and under it is my phone number checked.

Sent messages are blue bubble to all numbers except for two, which are green.

Sending messages take longer to show action than they used to on the Mac from the moment of sending but I suspect that may be a computer problem (maybe memory), I don't know.

As far as I can see I have checked everything you have mentioned and they appear to be correct. So still not resolved.

 

[Cory Cooper]

OK, thanks.

Here are the settings on my Mac:

Note: Mine lists my iPhone phone number, and Start new conversations from: my phone number is selected. Not sure if that is required for SMS, but it does work.

I am not sure if/why those settings changed on your Mac. I do know that when I message to a non-iPhone using SMS using my Mac, it will not go through unless my iPhone is powered on and not in airplane mode. If it is off or in airplane mode, the message's progress bar gets stuck and it fails to send.

Have you tried the steps here: Add or remove your phone number in Messages or FaceTime

Hope that helps,

C