Some Sources says,
Whatsapp is down because they're moving all data to the Facebook Servers
The company has confirmed to some sources in India that the service is indeed facing some issues and they are working towards fixing it. There is no word on how long it could take the company to restore the services.
When you open WhatsApp, it keeps trying to connect to the servers. It is quite similar to when you open the messaging app when there is no data connection.