Updates are issued as a full theme install. You download the file read the instructions and the install fails because the folder already exist. ya think? It's an update!
Why don't the instruction to install cover updates? am I supposed to uninstall the whole theme to install the updated theme?
I have tutorial for you, how to update the theme automatic?
https://oceanthemes.ticksy.com/article/6351/ And http://www.wpexplorer.com/envato-market-plugin-guide/