iMessages on iMac...Only affects One User...I send message, appears on iPHONE Message Thread, but iMac THEN minutes later says "Not Delivered"...

[jman995x]

Trying to figure out what is going on with the "Messages" app [Version 14.0 (6000)] on my iMac (Big Sur, 11.0.1):

So, in the past, I've been able to send and receive messages to anybody and everybody (obviously same Apple ID that is on my iPhone is what I'm logged into on my iMac).

However, about 2-3 weeks ago, ONE PERSON that I text with regularly....Messages on my iMac started acting oddly:

1. I would get her messages on my iPhone, but NOT my iMac (it's as if a wall was installed 2-3 weeks ago, and I can't receive any more messages to my iMac Messages app from this ONE PERSON).
2. I would send her messages on my iMAC, and they WOULD show up instantly on my iPhone Messages app, HOWEVER...
3. Minutes later, my iMac Messages would give me a "Not Delivered" error message (but I know they WOULD be delivered, because she would reply to whatever my question/statement was, and it would show up on my iPhone...but NOT my iMac).
4. It only happens with this ONE USER....Nobody else.

I've done the following:

1. Signed out of iMac Messages.
2. Turned off iPhone Messages.
3. Signed back into iMac Messages.
4. Turn iPhone Messages back on.
5. Confirmed that my phone number and email address(es) are correct on both my iMac and my iPhone.

Any thoughts why this would affect ONLY ONE USER, and in a Unidirectional manner?

Thanks,

J.

 

[Tumbleweed666]

I can't help but I have similar, I have a bank that sends me messages for 2FA and maybe 2 months ago, they stopped appearing on my iMac though they arrive on phone. It was convenient because I'm doing the login on my iMac.
Everyone else's messages (from iPhone) arrive on the iMac. Maybe the bank changed something at their end, just a thought, maybe your friend did?
Perhaps you could try noting down all her details (so as not to lose them) and then delete her as a contact and add back?