How to register test number when using WhatsApp Business API
I'm trying to send test message on WhatsApp Business API it took a day until I was shown a test number on "from" option now I need to register the test phone but don't know how.
the register link take me to the configuration page, but there is no option to register
Here is my WhatsApp account: 
You can't add any testing phone numbers, Facebook App by default provides one, that you can see in From dropdown,
You can add only productions phone numbers, follow the below ways,
You can find the option in your Facebook App > Getting Started under WhatsApp menu,
Second, you can add from Your Business Setting,
Read more about how to register a phone number in WhatsApp Business, https://developers.facebook.com/docs/whatsapp/phone-numbers
correct but this for production number, i'm ask about testing number that I get while creating the app
You can't add any testing business number, by default Facebook app provide one, that you an see in dropdown.
I also experienced this, it seems to be a bug in facebook itself or some lock in relation verified business, I did a test by creating a new business account and also a new application for this account , I activated whatsapp business and everything worked perfectly. But when I try to do the same procedure with an already verified account, the test number requests some kind of registration and also sends a notification that the test number was not approved. Unfortunately I haven't found any solution for this yet.
notification refused number