According to reports, it seems that the latest WhatsApp beta for Windows Phone has blocked the installation of the app onto the SD card. We’re not sure why WhatsApp has decided to block the ability, perhaps it might have something to do with performance issues, or maybe it could be legal issues, or maybe they just don’t want to utilize that feature.
It seems that users will also not be able to update the app to the next latest beta unless they move the app back onto the phone’s memory. We’re not sure if WhatsApp is planning on keeping this feature or if they will allow installation to SD card once the app comes out of beta, but for now if you’re testing the app, be sure to install it onto the phone’s memory, at least for now.