I had a similar problem when I was installing themes I had downloaded. The theme would download as a .zip file and when it was extracted/unpacked there would be another (sub folder) folder in there, and in side THAT folder would be the theme folder.
Every time I installed from the .zip file it would take the site down until I found out that it has to be installed from a main folder, not a sub folder.
So for you, if you downloaded it as a .zip file, extract everything from the zip into a separate folder, then find the main theme folder (with all of the files in it), then make a zip file of that main theme folder, then install that zip via WordPress.
It worked like a charm for me.