Not sure what you mean by downloaded and activated?
My host provides an automatic install of BuddyPress from my cpanel. I installed it from cpanel, set the site name and email then logged into the admin panel. All other themes work except your BuddyPress Default Home Theme. Its on the server in /themes/bphome and it shows up as a thumbnail in the ‘manage themes’ page but the site shows a blank page after I activate it.