I had tried to add a WhatsApp account in business manager settings. The guidelines in their helpcenter documentation stated that I could add a WhatsApp account from business manager settings. But in the business settings I could not find the add WhatsApp account button, except the Instagram account button. Is this feature not available in some countries or why would it not appear for some users.
I am facing this same issue but as per the documentation here, Facebook is releasing this feature gradually and is not currently available to all the users.
This feature is gradually rolling out and may not be available to you right now.
So far there is no clear statement afaik how the rollout process should exactly be. There is a page here where you can leave your data for consideration:
But I did it a month ago and still didn't get an answer.