The bootloader on these boards is notoriously picky about the hardware used for updates.
Using the wrong firmware can permanently damage the mainboard. Confirm the board number (printed on the PCB) and the panel ID. rsag7820 firmware upd
The RSAG7.820 series represents a family of printed circuit board assemblies (PCBAs) used by Hisense to handle processing, input/output video switching, and smart interface deployment (such as VIDAA OS). The bootloader on these boards is notoriously picky