Steam sharing not working?

A year ago I was able to get my brother to share his steam games with me via steam family sharing... First game I downloaded was Battlefield Bad Company 2 as I played it on my dads computer before that a lot... Anyways back to the point, I downloaded it I played it and was able to play it but after awhile I got interested in other games so I uninstalled it but now I want to play it again the only problem is when I try and download it (Yes via steam) It says "Steam was unable to verify ownership in order to request a product key. Please contact Steam Support. But steam isn't helpful so I thought I would ask you people on the internet... Also I can download it but I don't want to download a game that I can't play.