Thanks @Rydia. I actually got it back up and running by using a technique you provided to another user in July (G tech studio XL EV 24TB CRASH - #3 by Willem_Tiemersma).
Rydia WD StaffJ ul 19:
Willem, Here are the steps to try:
Open Terminal
Type in gspeed2util to launch CLI utility.
Enter the command: phydrv –a online –px and press return. (Where x is the physical drive ID i.e Slot 1-4 or 1-8)
Repeat the command for any drives listed as dead in the GUI.
The G logo should go white and the drive LED’s should change from red to blue.
Restart the Computer
After this the drive should mount and be usable. Make sure that if you have important data on here that it isn’t the only location the data is stored. If you feel the RAID is unstable at this point you can delete the array and create a new one, but the system should be fine after this.
Let us know if this doesn’t fix the issue.
