Sounds like a problem with the second WD My Cloud itself. Generally a white flashing (front) LED is displayed when one first applies power. See below for the front LED status indicators and their meanings from the WD My Cloud User Manual.
Probably couldn’t hurt to try another ethernet cable, to do a reset (see the following link for more information: How to reset a My Cloud device), if the problem persists then contact WD Support for additional support.
Front LED Status Indicator Meaning:
State: Power Off
Color: None
State Description: Displays if the device is unplugged.
State: Power On
Color: White
Appearance: Flashing
State Description: Displays when you first apply power to the unit.
State: Initializing
Color: White
Appearance: Solid
State Description: device has begun loading the Operating System (OS).
State: Ready
Color: Blue
Appearance: Solid
State Description: The OS is now ready.
State: Standby
Color: Blue
Appearance: Pulsing
State Description: Unit is in HDD standby mode.
State: Attention
Color: Yellow
Appearance: Blink
State Description: The following circumstances trigger this state:
• Disk thermal warning threshold exceeded (under or over temp)
• Network cable not inserted
State: Fault/action required
Color: Red
Appearance: Solid
State Description: The following faults trigger this state:
• Disk SMART failure
• Data volume does not exist
• System volume does not exist
• System thermal shutdown (75°C)
If there is a lot of content stored on the WD My Cloud it may take the unit quite a bit of time (hours) to scan the drive contents and enter a ready state (blue led).
Thanks for the detailed reply. Your instructions were great and I’ll be sure to keep them.
Luckily, I was able to get it to work by taking the first one off-line and going through the initial setup of the second WD drive. Then I renamed it so both had a different device name. Then and I powered them on one at a time and it worked. Not intuitive, but it worked.