This upgrade file works for the ZR08HF DVR. 

You can find your DVR's model number on the label at the bottom of your DVR. 

If your DVR's label is lost, please go to DVR's Main Menu - Information - System to take a photo to us, we will send the correct upgrade file to you.

You can follow up the guide below to upgrade the DVR:

1) You needn't open the upgrade file, please directly download the upgrade file and save it to your U-disk.  

(Please save the upgrade file rootfs-3521a in the root directory, not save it under any other folders.)

Note: to perform this process, you will want to use a USB 2.0 drive ideally 16 GB or less in size, formatted in FAT32.

Some customers have reported issues when downloading this file using the "Microsoft Edge" browser.

If the file was downloaded using the Microsoft Edge browser, this will cause the file to be converted to a text file, which can't be read by the DVR. We recommend using a different browser for this process.

In case it helps, here is a link to a Youtube video demonstrating the process: 

If you're unfamiliar with how to format a USB in FAT32, this video provides the steps: 

2) The file name must remain exactly as listed in the article for the DVR to recognize it as an update. 

It should be rootfs-3521a, if the file name is changed to rootfs-3521a(1), the upgrade will be failed.

3) Before starting to upgrade, please unplug the power supply and mouse, then plug the U-disk and re-plug the power supply. 

4) It can upgrade automatically as long as it has electricity, the upgrade process need to last several minutes, please be patient. 

If the upgrade is successful, please go to the DVR’s Main Menu > Information > System to check if the firmware version and Launch date have changed.

If the upgrade is failed, we suggest you change another U-disk or USB port to try.

Please let us know if you have any questions:

Support Email address:  service@zositech.com

Our Facebook:  https://www.facebook.com/ZosiTechnology/

Support center: support@zositechhelp.zendesk.com