Can't access iCloud Drive from my 2010 macbook pro.

Hi,

I can access iCloud Drive from the sidebar of my Yosemite mac mini. I can access iCD from iPhone and iPad. But, strange, I cannot access it from my 2010 macbook pro. It had Yosemite and, thinking it could be a system problem, I upgraded to El Capitan. But the problem persists. When I click in the iCloud Drive folder in the sidebar it keeps asking me to upgrade to iCloud Drive, something I already did. I'm starting to think that it could be some kind of permissions problem, but have no idea. Somebody has?

Thanks and sorry about the poor english.