thank you for your purchase. Do you use the WordPress installer (WordPress asdmin -> Appearance -> Themes -> add new -> upload)? Sometimes there is a restriction by the server for the file size you can upload, maybe thats the problem. Do you know how to upload a theme with a FTP software?
If you want, you can send us ( info @ 7theme . net ) the URL and the login for your WordPress installation, then we can install it for you.