Re-installing Whatsapp
A few questions to start. Does this happen with any other apps? Are you on Wifi or a Data connection?  Do you have the latest version of the play store?

You can try a few solutions.


Go to the app manager and clear the cache and data from "google play store" and "download manager".
uninstall updates from the google play store and download manager if they exist.
boot into recovery and clear the cache and dalvik.  To do this hold the volume up button when turning the phone on


Here is a little blurb explaining that it is safe to do and won't delete your data or apps
https://www.quora.com/I-want-to-wipe-dalvik-cache-on-my-phone-Will-this-delete-my-apps-or-data


Lastly you can try logging out of your Google account and back in


Give that a try and see if it helps
-Asloss