Registration API is only supported in certain payment methods.

Credit Cards
Supported. Used to register card information to be captured at a later date.
Direct Debit
Not supported.
PIX
Not Supported
PayPal
Not supported.
Boleto
Not supported.

Registrations API is used to register credit card information for use in a future payment. Difference between Authorization API is that it does not have an amount to block for future deduction.

Below is the summary of the Registration API's use case.

Send a POST request to /rest/register with the parameters mentioned in the list below.
Redirect the end user to the returned URL.
End user inputs credit card data and gets redirected back to Merchant’s shop. In case of success, to success_url, in case of an error, to an error_url.
Transaction status should now be registered. Keep the transaction_id for use in original_transaction_id field in further requests.
Make a payment request Payment API. Fill original_transaction_id= with the ID from the Registration call above in the request body. Set recurring=1 if you intend to make recurring payments.