The disk is offline because of policy set by an administrator
diskpart.exe
diskpart> san
SAN Policy: Offline Shared
diskpart> san policy=OnlineAll
Diskpart successfully changed the SAN policy for the current operating system.
diskpart>list disk
Disk Status Size Free Dyn Gpt
--------------- ------------------ ----------- ----------
Disk 0 Online 40 GB 0 B
*Disk 1 Offline 60 GB 1024 KB
diskpart>select disk 1
Disk 1 is now the selected disk
diskpart>attributes disk clear readonly
disk attributes cleared successfully
diskpart>attributes disk
current read-only state: no
boot disk: no
pagefile disk: no
hibernation file disk: no
crashdump disk: no
clustered disk: no
diskpart>online disk
diskpart successfully onlined the selected disk