Same workgroup PC cannot see the shares but can see the WDMYCLOUDMIRROR!

My Cloud OS 3 Personal & Network Attached Storage My Cloud Mirror
4

Had a similar issue. See this thread for possible help in resolving your issue:

http://community.wd.com/t5/WD-My-Cloud/Can-t-access-private-share-from-a-Windows-7-PC/td-p/702380