Thank you for your reply, .
Hi. Welcome to the Nokia Support Discussions.
It is because the WhatsApp app has been temporarily removed from the Windows Phone Store due to a recently discovered issue with how notifications are handled on Windows Phone 8.0 Update 3. We are in the process of working with WhatsApp to resolve the issue as quickly as possible. Thank you for your patience and sorry for the inconvenience.
Moderator's note: The subject was edited as the post was merged to the most appropriate thread.