This guide will tell you, How To Fix The Notifications Not Working On PS5.
First, you have to go to the home page of your PlayStation and navigate to settings in the top right corner of your screen. After that, click on User and Account and select Privacy from the left side of your screen. Then you need to click on View to customize your privacy settings.
Scroll down to Communication and Multiplayer and you will find an option “Who can ask to be your friend.” You have to set it to Friends of Friends or to Anyone and then you will receive any friend requests notification. After that, set the “who can interact with you through parties, messages” option to Friends of Friends or Anyone and then you will start receiving the notifications.
Now go back to the settings page and scroll down to select Notifications. You have to make sure that your pop-up notifications are turned ON. After this, come down to “When Friends Go Online” and set the notification setting for this according to your choice.
After this, you have to select friends that notify you. From here, you can choose the friends whose notifications you want when they become online.