You can follow up the below steps to reset the NVR:
(1). Please format your USB-disk to FAT32
(2). You can directly download and save the file to your USB-disk from the attachment.
Please note: please directly save the file in the root directory of your USB-disk, not save it under any folders.
(3). Please insert the USB-disk to the NVR's USB ports
(4). Please connect the power supply to the NVR, once the NVR system starts, you will hear "beep" sound.
The system will reboot itself several minutes later, please be patient.
Please note: this file can only be used once, you need to re-save it to your USB-disk next time.
If this can't help you, please feel free to contact us.