We have in the past (and as much as time permits now) make an effort to help (hopefully!) and offer ideas to people here but I would be really intrigued to know what % of people who come on here asking for ‘help with rejected’ actually go on to have the same files approved…
Form experience I am not convinced it is that larger proportion.
Opt 1: In your download page click download & select ‘installable WordPress File Only’ & use this (if you can’t see this then it is not a WP theme).
Opt 2: Are you sure you have the WP theme and NOT a HTML file?
Opt 3: Are you using your own hosting and domain NOT WordPress.com
Opt 4: Unzip the theme folder and use ftp to install it