What to do if hard disk drive can't be recognized?
You can format the hard drive before using it.
If DVR or NVR can't recognize HDD, we can try methods below.
1) If hard drive is not from us, please make sure your hard drive meets all requirements in the link below.
You can refer to this for the requirements for hard drive: http://techage.com/knowledgecon.php?article_id=121
2) Open the cover of DVR/NVR. Uninstall and install HDD for several times.
Note: Before installing the hard drive disk, please power off the system if it is on.
3) Install hard drive and put hard drive close to your ear to check if you can hear some noise. One hour later, use hand to touch hard drive to check if it is warm. If you can not hear any sound and surface of hard drive is not warm, it can prove hard drive is not even powered up. Please share us the result.
4) Unplug DVR or NVR from power and plug again.
5) Restore DVR or NVR to factory setting.
6) Change an adapter of DVR/NVR.
7) Try a spare DVR/NVR or HDD if you have.