To activate Facebook birthday notifications on desktop, go to Facebook Settings, click on Notifications, enable Birthdays, and choose your preferred notification method (Email or SMS).
To activate Facebook birthday notifications on mobile, open the Facebook app, go to Settings, tap on Notifications, select Birthdays, and enable your preferred notification method (Facebook, Push, Email or SMS).
To turn off Facebook birthday notifications, go to Notification Settings, select Birthday, and disable the 'Allow Notifications on Facebook' option.
If birthday notifications are not showing on Facebook, ensure the notification settings are enabled, check for any server outages, clear browser cache & cookies, and ensure the Facebook app is updated.