First, let's see if it's the hardware or software causing the issue. I assume you have tried to reboot and got nowhere. For the next step, power down, remove the drives (labeling the slots they came from) and power up with no drives. Does RAIDar show the NAS with a "No disks" status?
If not, it's not a good sign. If you can see it, power down and put the drives back in, then power up to the boot menu and try an OS install. If you did not see it in RAIDar with no drives installed, a USB recovery might help, but it's probably a hardware problem.
If you can't get to the boot menu with your original array installed, remove all the drives with power off and put in just one drive that is not part of your array. See if that works, either without intervention or via the boot menu. If it works this way, you probably have one drive that is so messed up it's bringing down the whole NAS.
If it''s a drive that looks like it could be the peoblem, then use manufacturers tools (e.g. SeaTools) to check the drives. If one is bad, return just the others to the NAS with power off and see if it now boots properly.
This is a long list. If you get lost or unexpected results at any point, come back and give an update. We'll see if we can help get you back on the road.
Do you have a backup of the data? If not, then If you have access to a windows PC, you can connect disk 1 of the NAS to the PC (using either the internal SATA connections in the PC or a USB->SATA adapter). R-linux for Windows is free software that can read the data volume of the NAS. http://www.r-tt.com/free_linux_recovery/ That will hopefully let you offload the data.
Also, you can see if RAIDar discovers the NAS with no disks inserted (it should detect it and give you a "no disks" status). That would let us know that the NAS ethernet card is still working.
