Hi Haritha,
Check whether the hierarchies are displayed for the corresponding data source in ERP ssystem.
You can check the hierarchies from tcode SE38--> program name "RSA1HCAT"--> enter language and your data source "0ORGUNIT_HR01_HIER" and execute the program . here youcan see hierachy as tree and check whether you have any parent/child nodes present or not.
If data is present against that data source then check in BW system whether the preocess chain has save hierarchy step or not. If you dont have this step then the hierarchies are not saved.
You can add it by following stepos mentioned in below link.
http://help.sap.com/saphelp_nw04/helpdata/en/3d/320e3d89195c59e10000000a114084/frameset.htm
Let me know if your problem still presists.
Srikanth