You may receive a "WhatsApp number linked to another Facebook business" error message when trying to connect your Facebook Page to your WhatsApp account. This may be because your WhatsApp phone number is already linked to another Facebook business. In this case, you'll have to remove your WhatsApp number as a business asset in Meta Business Suite.
You'll need to have admin permissions for the business that lists your WhatsApp Business account as an asset.
Now that your number is no longer connected to the other business, you can go back and connect the desired Page to WhatsApp from your Facebook Page or from the WhatsApp Business app.