Hi my name is ***** ***** I will be the expert working with you today to help and resolve the problem you have posted.
What error message you get from Whatsapp when you try to sign in.
Uninstall Whats app from the phone/tab and then restart the device try to download and install it back from the App Store. Let me know how it goes?
on the home page look for settings and click on it.
Scroll down and select Apps and then you will see whatsapp in the list select and remove it.
you must be having a google account try to login using the account.
I believe i have not delayed in answering your question. Did you follow the steps i gave. You cannot sign in to an android device without having a google account and if you do not have one you need to create one to use it.
May I also welcome you to JustAnswer and thank you for using us.
On what device make and model are you having this problem on?
Ok no problem. I am forwarding your request to relevant people who can handle refunds.