My 2 cents:
- Ensure that firmware & display software are matching.
- Ensure that the SD-card with the new firmware is formatted properly & not write protected.
- A successful update will be indicated by a changed file name of the firmware installation file from “firmware.bin” to “firmware.CUR”. In that case at least the MPU & its seven pins that drive the SD-card interface on your motherboard are still alive…
Here you’ll find a documentation of all SV04 pins & connections on the motherboard. Checking out for +5V & +3.3V should help. Additionally, you could connect your SV04 to a PC via USB-cable. This will bring sufficient power to boot up motherboard & run the display.
Good luck!
Björn