It’s really embarrassing for us, that our theme update broke your whole site. We tried it in our local server and we couldn’t get such issue while updating the theme. Even we tried it in our demo site and update successfully.
Have you made any changes in our original theme files, before you make the update? Most of the case it occurs if you made changed any theme files.
You can try it once by deleting the previous theme and install & active new Envy Blog theme from WordPress.org Themes directory.