Due to the COVID-19 landscape, Visa made the announcement that signature retrieval requests may only be placed for transactions that took place before May 12, 2020. As of October 16, 2020 signatures will be optional for all transactions, therefore retrieval requests will no longer be permitted. For more information please see the attached release provided by Visa.
Visa is encouraging merchants to discontinue requiring signatures on transactions to improve the customer's experience. Within your terminal settings you may turn off the signature prompt entirely to implement a No Signature Policy.