Got a brand new Iphone 12 yesterday. I can send text messages to my wife (who owns a pixel4a) but when she replies I don't get her messages (it's not a notification problem, I simply don't get any messages from her).
When I send messages to the iphone from my professional mobile phone (a samsung), I receive them (with notification) consistently.
When I installed whatsapp on the iphone12 I received the verification text message as well. And I received commercial messages from my provider (Orange) last night. So, it looks like I receive messages from most of my contacts, but I can't get messages from others (again, not a notification problem, but a reception problem). That's weird.
I upgraded to 14.3 last night to no avail.
I made a full reset (settings + content) this morning and reinstalled from scratch without using my icloud account, didn't solve the problem either.
I've called Apple Support, shared my screen, send them analysis data, they made some remote investigation and asked me to open a case at my provider, and then come back to them with the case number so that Apple could call Orange and investigate further.
I'll try to turn off Imessage on my ipad pro and look if it makes things better, as some seem to have solved the issue that way.
Very disappointed to have problems without such a basic - but very important - feature :-(
**** EDIT : I managed to solve this issue by myself
I solved my problem by myself, that was tricky. I couldn't receive on my iphone 12 the text messages my wife sent me from her pixel, because my previous phone was a android phone with google chat enabled.
After I switched my phone for a iphone 12, google chat was still enabled for my phone number in the google/android ecosystem. The messages my wife sent me were sent as 'google chat messages', not mms/sms messages, and obviously an iphone is not part of the google chat system.
As soon as I de-registered my phone number from Google chat, the messages my wife sent me turned to classic sms/mms messages (not google chat message anymore) and ... bingo... I saw them pop on my screen.
So in my case it was a problem due to switching from google/android to apple ecosystem.
Some useful information here :
https://www.androidcentral.com/heres-how--deregister-your-phone-number-google-from-rcs-chat