I recently replaced drive 7 in a Pegasus 2 R8 Raid 5 with a new drive identical to the original, this is my third "new replacement drive".  I am not able to rebuild the logical drive as the new drive does not appear in the physical drives list.  The contents of this RAID are no longer critical as I was able to transfer all data to a new Pegasus 2 R6 before trying to replace the non functioning drive.

I also saw a script that can access the drives through terminal, however this technique didn't work either.