cannot see baseline to stage in vum

Hello,

I am trying to update ESXi5.1 to 5.5 using vcenter update manager.

I have uploaded /imported an DELL ESXi 5.5 ISO to a base line but even after scan and stage I dont see any baseline to select for staging.

also tried uploading new ESXi5.5 iso from vmware. my vcenter and update manager are already running 5.5.

Thanks in advance