What are the possible reasons for a number registration to fail?

The number has not been fully deleted from the WhatsApp app/ WhatsApp Business account. Follow the instruction below to remove the number completely from WhatsApp app/ WhatsApp Business.

It requires deleting the WhatsApp account associated with the phone number.

Migrating your number, all incoming messages will be queued by WhatsApp servers and delivered after a successful migration.

There is no way back. All existing messages, groups, and chat history cannot be imported once the number has been upgraded to the WhatsApp API. Your former WhatsApp app can not be used afterward.

Step1: Open WhatsApp Messenger or WhatsApp Business app on your device.

Step 2: Navigate to the Settings page. Select Account.

Step 3: Select Delete my account.

Step 4: Enter the phone number, and press "Delete My Account"

Step 5: WhatsApp will delete the associated WhatsApp account. The number will be immediately available for number registration.