The update changed my theme from Twenty Thirteen to Twenty Fourteen, and now nothing is visible on the site. I also have error messages saying the stylesheets for 2012, 2013, and 2014 themes are missing. I tried to 'reinstall' 2013, but since I already have 2013, I can't do that. Where do I get stylesheets, and where should I store them for WP to see them? Unfortunately, I am brand new to WordPress (user for about a week). If anyone has a suggestion, please dumb it down appropriately. Thanks.