Are you currently able to access the , or is it stuck on a boot logo ? ZR04BE_V1.1.5 Upgrade File_rootfs-hi3520d - Zosi Support
If your device is a Zosi or Zosi-compatible model, they provide several rootfs-hi3520d upgrade files, such as for the ZR04GM or ZR04GA . Download Firmware DVR 5004XVR HI3520D Backup rar
Save the file directly to the root directory of the USB (not inside a folder). Are you currently able to access the ,
Plug it into the DVR and go to Main Menu > Information > System > Upgrade (or similar path depending on your interface). they provide several rootfs-hi3520d upgrade files