Some of the UniFi UNVR’s have system files on a USB drive. There seem to be a number of the drives failing recently, rendering the UNVR inoperable. Fortunately it is easy to replace. The following steps should preserve the video recordings.

https://community.ui.com/questions/UNVR-stopped-responding-just-white-flashing-light/a051f869-8349-4a2a-a72a-ce3a8aa8c759

Steps to recover UNVR

1. Power off the UNVR
2. Remove the USB drive (use a heat gun or screw driver to break the glue that is holding the USB drive)
3. Install new USB drive
4. Temporarily remove UNVR HDDs (this may not be necessary, but rather be safe then sorry.)
5. Boot UNVR with new USB drive. (Give it a little time to format and copy contents to the new USB drive. Should not take more then 30 minutes.)
6. Setup the UNVR like it was before
7. Power off the UNVR again
8. Reinstall the HDD’s
9. Power on the UNVR
10. Log in and reconfigure the users

Note on Recovery

You could potentially mount the failed or failing USB drive on a Linux machine copy off a UniFi backup. Unfortunately, the UniFi Protect backup does not preserve the users. Just the video groups. You will probably have to resend invites to users.

Note on the video storage drives

It sounds like the UniFi Protect system will try to read the drives and if it can preserve the data or read the raid information it will try to use that. That is what it sounds like at least from the forums. More info on drive management.

https://help.ui.com/hc/en-us/articles/360037340954-UniFi-Hard-drive-compatibility-and-management#h_01F8QE56P7EY1P9FMTZHFZD463