Here is my experience:
Notifications sound out and are sent to my phone but do not wake my locked screen and display them. However they are sitting there when I unlock it.
Affects all apps, notably SMS messages, MS Authenticator, FB Messenger, Whatsapp, Yahoo app emails.
Weirdly the issue 5% of the time goes away and makes you think you've solved it, only to return again 1 hour later.
I upgraded to IOS 18.2.1 - no change
I reset network settings where it worked again for a brief time afterwards. (about 30min and 10 notifications)
I reset all settings - Very painful process of re-allowing all apps to send notifications again. But made no difference.
I reinstalled some apps - made no difference
I spoke with Apple and they remoted into my device and confirmed all settings were correct.
They checked with their engineering team and confirmed this is a known issue they have not resolved yet. They advised me they have been working on this since the release of IOS 18.1
They advised me all I can do is wait for the fix. Sigh.....
Then about a week or so later.....
Weirdly enough... I have an update on my situation.
I changed iPhone protective cases and all the notifications work now.
Makes no sense... Very strange as I had tested this initially by removing it. and the issue was still there.
So anyway just thought I'd mention this incase anyone else wants to try it.
Originally I had one of these ESR cases from Amazon with the tempered glass cover over the front that clicks into the back cover. I replaced it because the touch screen sensitivity was poor and I just didn't like the added bulkyness.
ESR for iPhone 14 Pro Max Case, Compatible with MagSafe, Full-Body Military-Grade Drop Proof Case for iPhone 14 Pro Max with Built-in 9H+ Tempered Glass Screen Protector and Stand, Clear Black
So it's possible this was interfering with the screen in some way or touching one of the buttons.
Anyway - All notification back to normal now.. TBH though I enjoyed the quiet for a little while... Might have to rethink my notifications altogether and tune them way down...