Buffalo TS-QVHL Raid 6 replaced drive rebuild never ends...

[alirezafar]

Hello everyone,
I have a 4TB RAID6 Buffalo NAS TS-QVHL which its HDD1 failed few days ago. So I got a replacement Seagate HDD and replaced it just as it was directed in the manual. But the problem is that after I pressed and hold the function button in order to rebuild even though the red LCD is gone and its blue but the rebuild process never ends. Now is close to 20 hours that the NAS is doing something and not finished yet. When I try to check the status through the web interface this is what i get and never changed in past 20 hours.https://www.dropbox.com/s/u1guffz23kdz138/Screenshot%202016-01-17%2002.54.59.png?preview=Screenshot+2016-01-17+02.54.59.png
So I'd appreciate if someone guide me if there is anything that I can do to resolve this issue or if its normal also let me know.
BTW the NAS is not accessible either, so I have no way to access my files.

Thanks in advance,
Alireza