Apparently the latest version will determine if an upgrade is required automatically. Please see:
Version 2.0.0 no longer requires that a drop down is used to indicate that an upgrade is to be performed. The plugin now can determine if an upgrade is required automatically. This change not only streamlines the process for many users, it also fixed compatibility issues that some users experienced with older versions.
How do I upgrade a theme?
Download the latest zip file for your theme.
Log into your WordPress site.
Go to Appearance > Themes.
Click the “Add New” button at the top of the page.
Click the “Upload Theme” button at the top of the page.
Select the zip file with the new theme version to install.
Click the “Install Now” button.
https://wordpress.org/plugins/easy-theme-and-plugin-upgrades/faq/
Thanks