How to fix the “Broken theme and/or stylesheets missing” error message
A common issue that can occur with users new to installing WordPress themes is a “Broken theme and/or stylesheets missing” error message being displayed when trying to upload or activate the theme. This error message does not mean that the theme you have purchased is broken, it simply means it has been uploaded incorrectly. The exact error message may vary, but will typically include the words, ‘Broken Theme’ or ‘Stylesheet Missing’.
Please make sure you are uploading only the installable theme which is called theme_name.zip. When you download the theme from your ThemeForest downloads it will give you 2 choices one is to download the full zip which you will need to extract to locate the theme and the other one is just the installable theme.
So please pay close attention to this because most likely you upload the full zip which contains other files like documentation.