After July 1, 2019, WhatsApp may not be accessible in Microsoft Store. A fresh data on Windows Phone was updated on the WatsApp FAQ page (via OnMSFT):
This phrase is somewhat vague because the term “might” is used, but the WhatsApp appears probably will be deleted in a comparatively short time from the Microsoft Store.
The Windows Phone version of WhatsApp has already been known to lose assistance by the end of 2019. As well as losing support for the Windows Phone version, Android versions 2.3.7 and older as well as iOS 7 and older are not endorsed.
Once a WhatsApp version is not endorsed, characteristics may no longer work because it has not been created. If your Windows phone has WhatsApp already, it could operate for a while after it ends, but could stop working.