Whatsapp on ultra Apple Watch
How can re install WhatsApp on my ultra Apple Watch
iPhone 7 Plus, iOS 14
Question marked as
You can't reinstall something you didn't have to begin with. Meta, the parent company of WhatsApp has never released an Apple Watch version of WhatsApp. They would have to make one as Apple doesn't own them and has no control over their apps.
You can contact the developer of WhatsApp and let them know this is something you like --> How to contact an app developer - Apple Support