Place the file in: C:\Users\[YourUsername]\.switch\prod.keys
If you use the or Ryujinx emulators, they also require keys. You can often find their prod.keys file in C:\Users\YourName\AppData\Roaming\yuzu\keys\ (Yuzu) or the Ryujinx system folder. Copy that file to hactool’s location. However, note that hactool requires a full keyset (including keys that emulators may not store), so this may still fail. hactool prodkeys does not exist fixed