Welcome to Nokia discussions board!
I advise you to uninstall Whatsapp and download it again from my stuff in Nokia Store.
As for the issue with Nokia Store on your device, it will be fixed by resetting your phone. I strongly advise you to back up your data on your computer beforehand using Nokia Suite, because the hard-reset will erase it from your device. Once your data is safe, you can format your phone. To do so, please enter the code *#7370# on your keyboard. The default lock code is 12345. If an update is available for Nokia Store, please download it. You will then be able to access Nokia Store again.
Let us know how you get on and feel free to post any other questions you may have.
mine is also not working everytime i download it it says
java.io.IOException:4-Error in HTTP operation
what does this mean and how can i sort the problem out