I noticed this issue sometime after upgrading my iPhone 7 to Ver 14. No notifications for messages or emails. I tried everything. My Mac is not the problem because I rarely use it. When not in use, it is off. So with a iPhone 7, and a Watch 4, nothing on either device. I used to get notifications on both. When someone calls me it rings both devices. But nothing for messages or emails. I gave up, thinking the iPhone 7 was broke some how.
So I bought a iPhone 12 brand new, thinking that would fix the problem. It did not, same problem. Complained to Apple, then I saw this thread. One user said, "turn off Bluetooth", did that, and lo and behold, I get notifications on the phone. Turn Bluetooth back on and no notifications. Turn it back off and notifications work. That is unacceptable, Watch needs to be paired with the phone so need Bluetooth. Saw another post that stated, goto the watch app on your phone, tap "Notifications" then scroll down to "Messages" tap that, then "Custom" then "Notifications Off" and that worked. The phone gets notifications but not the watch. Check it out if you can live without notifications on your watch.