WD Red Plus Not Compatible?

I just purchased a WD Red Plus hard drive to replace a failed drive, and my Drobo 5N does not recognize it. The plug in side if the drive does not look like the rest of my drives. Any ideas why the WD Red Plus would not function in my Drobo?

The plain WD Red is known to be incompatible owing to using SMR, this is the first time I’ve heard of any issue with a Red Plus which uses CMR. How long are you leaving it in before deciding it’s not recognised? It can take a little while sometimes worth leaving it 5 or 10 minutes, & possibly rebooting the unit and leaving it that again to encourage it to notice.

If it still doesn’t, check out you haven’t got a dud drive using a PC.

I have left it in the bay for a few hours, and the Drobo continues to flash red, indicating a drive failure. The plug in side looks entirely different than my other Drives, as it only has a two pin connector, but there is nothing on the packaging that indicates why it would be different or have a different purpose.

Here is a list of known WD drives and whether they are CMR or SMR.

Also see:
https://myproducts.drobo.com/knowledge/s3/retrieve?qs=fc7d7ac392851d091a0a2be632329282b3b769820e6144d55b898f9a7ead1a68

This may also be helpful to ensure the drive is fully seated:

If the lights on Drobo are Not flashing (if the lights are flashing Green/Yellow, let this process finish), please do the following:

NOTE : Do NOT remove or insert drives while the Drobo is powered on

  • Shutdown Drobo using Drobo Dashboard > Tools > Shutdown
  • When Drobo is completely powered OFF, gently eject the drives and re-seat. ​​Drive(s) vary in size, for this reason, to ensure the drives are securely seated please review: Installing Drives in Drobo. As described in the video, push the drive into the slot.
  • If you are using an mSATA card, remove this from bottom of unit.
  • Ensure the serial number or label on the drive(s) are facing the front and are right side up.
  • Push drive further in with your right thumb close to the gray tab. At the same time, move the gray tab to the right with your left hand.
  • Once the drives are securely seated, power On the Drobo​.
  • If still not detected, send us photo of front of Drobo with Drobo powered On, Face Plate off and drives installed

NOTE :
If you are using a 4, 5 or 8 Bay Drobo, ensure you are NOT using SAS drives.
If the drive has a label, the label must be facing the front and right side up as outlined in video (above); How to install drives into Drobo

Reference:
How to install drives into Drobo
How to Install mSATA
Drives Recommended for use in Drobo