How to Fix the Missing Stylesheet Error?

That’s a common issue caused by not uploading the correct zip file when trying to install the theme. Go back to http://themeforest.net/downloads and when clicking the Download button, choose the “Installable WordPress file only“.

Here is an article form the Envato’s documentation that might help you:

https://help.market.envato.com/hc/en-us/articles/202821510-Theme-is-missing-the-style-css-stylesheet-error