You may not receive notifications if you did not authorize them when you first logged in.
On iPhone :
go to phone Settings
Notifications
Bilder
Allow notifications
For Android (the process may vary from device to device):
Phone Settings
App Settings
All Apps
Bilder
Enable Notifications.
Once activated in phone settings, go to app settings and enable the feature (Home β Swipe right from the left edge of the screen β Settings).