The is not a separate software download. Rather, it is a procedural correction involving USB enumeration, driver conflicts, and timing. AppleTech752 documented this in community forums and video tutorials after users repeatedly encountered Error 61 when trying to enter "PWND DFU" mode (a pwned state allowing unsigned code execution).

were plagued by the frustrating "Failed to Send/Retrieve Response" error, which halted iCloud and passcode bypass attempts. The Breakthrough Fix Released in May 2021, Sliver 6.1

Before installing new drivers, you must ensure old or corrupt drivers are removed.

"Error -61: Unable to send the final data packet. Device rejected command."