after updating to 18.3.1 iOS
the whatsapp is not detecting the Microsoft Swift keyboard, reamaining apps detects them but not only whatsapp
could be issue specific to microsoft app keyboard bro. when you try to switch to microsoft keyboard, it appears but unable to show the keys you type correct?
no, the app itself not showing inside whatsapp
is the keyboard enabled under settings - general - keyboards and full permission given? you can open microsoft keyboard app and check once any permission issue present. based on that you can enable and then the keyboard will start showing on apps including whatsapp.