A lot of iPhone users are having issues with the Messages app, and most of the complaints reportedly come from iPhone 12
The problem seems to affect both individual and group chats, with some users saying they don't get notifications when a new message arrives, and others complaining they are not getting texts from some senders at all, as reported by MacRumors
Some users also say that they are unable to see messages sent by Android users in group chats. A few iPhone owners say that messages are delivered with a delay.
Official Apple Support Community
threads are also filled with similar complaints. The problem might not necessarily be specific to newer iPhone models, and might instead be related to iOS 14.1 and iOS 14.2.
A couple of solutions have been proposed by affected users, such as downloading the Verizon Message+ app if you are on Verizon, or resetting network settings, but they do not work for everyone.
Apple Support has reportedly told some users that this is a carrier issue. The problem will likely be fixed with a software update.
Here is what one user had to say regarding the messages bug:
Upgrade to 12 Pro and passed down my 11 to my wife. Few days later she asked why I wasn't responding to the group message thread we have for my family and then I noticed I was not getting them.
Did all the regular troubleshooting, even reset and setup device as new. I was running the iOS 14.2 beta on the 11 prior to update and did not notice the issue. Even now my wife has the 11 running the 14.2 beta and no issues there. T-mobile checked all account settings and it appeared fine, they recommended getting a new 5G SIM card which I did last week but issues remain.
At this point I have to assume the problem is one of two possibilities:
1. there is a bug in iOS 14 that is only related to the new devices (iPhone 12) or
2. the new cellular radios/chips in the iPhone 12 are having issues with all carriers and this needs to be worked out between the carriers and apple