A RAID 5 4T disk erro of MSA2050

[Ioiris]

There was a 4T disk error which bothered me for many days.

We team borrowed a same disk and replaced the error one,then the new disk light showed green.

But the MSA 2050 Still showed  RAID 5 not available,the new disk could't rebuild automatically.

We tried to add Global Spare by the "Pool theme", but to our surprise, "Add disk group" option couldn't be selected.

In the "System theme" panel we can find the disk which group was not assigned with 0 spare, other normal two disks had added group dgA01, and added into pool A.

To the MSA system, i'm a freshman,could your technical experts can give me some assist?