: If the DVR won't boot, open the casing and look for the printed hardware model and version directly on the board.
: If your DVR is from a major brand, check their official sites like EasternCCTV or Lorex for tools and extracted flash files. How to Identify the Correct File Download FLASH DUMP DVR HI3521A V123 1080N16 rar
Finding a specific "flash dump" for a HiSilicon-based DVR like the HI3521A V123 1080N16 : If the DVR won't boot, open the
: Insert the drive into the DVR's USB port and navigate to System > Maintenance > Upgrade (the exact path varies by brand). V4.02.R11 H.264/H.265 DVR/NVR Firmware Download : If the DVR won't boot
: If prompted for a password during the upgrade process, many systems use a default like 123456 . General Flashing Procedure Format USB : Use a flash drive formatted to FAT32 .