I just finished programming for the embedded signup process + registering the number + webhook subscription... and then tested it with a phone number of mine: it worked fine!

Then, for testing purposes, I de-registered the number and removed the app manually from that number on the META's Whatsapp dashboard.

So I am trying to register it again but I get this error now: OAuth "Facebook Platform" "invalid_request" "(#133005) Two step verification PIN Mismatch"

It is weird because I am using the same PIN as before.

What can the problem be?

I've tried manually changing the PIN on the phone dashboard. The two factor authentication is set to be active, but the "CHANGE PIN" button is disabled. Next to it, there's an error saying I need to activate the 2 steps authentication, for which I need to verify my business, which I can't do because it is a test business, not a real one. Is this the issue?