Volume not connected

HI...

Greetings of the day..

I have Anextek NAS server , this server have 2 expantion boxes . In first expantion C, D drive and 2nd expansion E, F drive is there,
In this server we had configured RAID-5 ,in first expansion (Volume 1, volume 2) and 2nd expansion (Volume 3, volume 4).

In 2nd expansion volume 4 its not getting connected. I checked hard drives through telnet , its connected.

How to check the status of the 4'th volume and get the volume back.

Response is appreciated.

Thank's & regards,

Narsing.