If you find that you are not getting notifications for Google + then you will need to go through the below and check the settings are
How to Fix
Go to “Settings” then select “Accounts”. From there select the option entitled “Google” and then “Google Plus”. Once in this heading
select the option for “Notifications”. If the setting is set to ON then you should be receiving the notifications.
To check that notifications are set up on other functions you will need to access that application, click the settings button for that app
(located bottom right of the screen) and select the option within.
Note: Not all applications have this function.