Castles UPT1000F: accessing Program Manager or supported application-loading mode

I am repurposing a Castles UPT1000F that still runs its existing preinstalled software. A USB keyboard connected to the documented host interface is detected at the hardware level—the lock-key LED responds—but the running application ignores key input. I also connected the documented three-wire serial harness through a USB-to-serial adapter to Windows; the COM port opens normally, but repeated captures spanning a normal power cycle return zero bytes. A direct USB connection likewise exposes no CDC, HID, storage, or other maintenance interface to Windows. Does anyone have model-specific documentation or firsthand experience entering Program Manager or maintenance mode, or invoking the supported application-loading workflow on a UPT1000F?