Home Network - I can"share screen" but not "connect as" to a powerbook on my home network?

What settings have I screwed up so that I can "share screen" but not "connect as" to a powerbook on my home network? Other desktops and laptops are no problem. The MBP will hook up to other macs in the network and my NAS. Somehow or other my ROON software sees the files in the desktop .

Macbook - OS 10.9.5 - wifi

Most others OS 10.10.5

Thanks,

David - Dallas