I can't view your activity on Steam itself either. The new privacy settings they've implemented seem to have some issues - another user set theirs to public as well yet the profile is still showing up as private :/ I will report the issue to Valve - nothing else I can really do about it unfortunately.
edit: That other user's profile finally switched to public so maybe it just takes some time...
I figured out why some folks are having issues with the new privacy settings. Turns out, if you opt to hide your playtime it completely blocks recent activity from being viewed on Steam, even if you've set your game details to public. I have no idea why this would depend on the playtime setting, but it does.
So for proper tracking on here you will need to leave the playtime setting public, unless Valve fixes this.