See and post to the correct subforum for the PR4100, where users more familiar with the PR4100 may be able to assist.
OS5 My Cloud Pro Series
http://wdstagingsplit.staged-by-discourse.com/c/os5/my-cloud-pro-series/256
You can search through that subforum using the forum search feature (magnifying glass icon top right) to see if anyone else has experienced a similar issue.
Relevant WD Support documents from the Knowledge Base link at top of page:
LED Status, Alert Codes, Descriptions, and Email Notifications for WD My Cloud
My Cloud Solid and Blinking Red Power and Drive LED Status Information
