Hello petunia1006,
Ensuring notifications are coming through on your iPhone is extremely important, and you've come to a great place for help. iOS 14.2 has recently been released, and it is recommended to update to the latest iOS version. You can find the steps for updating in the following article.
Update your iPhone, iPad, or iPod touch
If you continue to have issues after updating do you notice if the notifications may be forwarded to an Apple Watch if in use? The reason we ask is if you have an Apple Watch, and the iPhone is not in use you'll see the notifications forwarded to the Apple Watch.
Also, verify that Do Not Disturb isn't contributing to the issue. You can find great tips on verifying Do Not Disturb Settings in the following article.
Use Do No Disturb on your iPhone, iPad, and iPod touch
Have a great day!