Why doesn't the watch give alerts after I've set messages alerts for WhatsApp, Facebook, etc.?

The following are necessary conditions for the watch to display WhatsApp, Facebook, and other App message notifications: 

1. Make sure that your mobile phone can receive message in the notification bar. If the notification bar of the mobile phone does not receive a message, go to the system settings to turn on WhatsApp and Facebook notifications. 

2. The watch needs to be always connected to the mobile phone, and the Bluetooth needs to be always turned on. 

If the watch still can't receive alerts after you perform the above operations, try to turn the mobile phone Bluetooth off and on once.