Installing firmware via USB is the standard way to recover or update these "China Universal" boards: Use a USB flash drive formatted to FAT32 .
Provides a specific RR8501.C031F firmware file (approx. 23 MB). Download RR8501 C031F 1366x768 USB rar
Offers various resolution versions for the RR8501 series , including the 1366x768 PNL NORMAL build. Installing firmware via USB is the standard way