Cannot update to version 4.0.20

Thanks for reaching out, this error can sometimes occur between your website and the update WP.org servers timing out.

Our recommendation, go ahead and deactivate and delete the current version you are running. Search and install and activate a new version of 4.0.20. All the settings will be restored. You can also try the update again, without the full deactivation and deletion. We suspect either one of these approaches will resolve that timeout issue that occurred originally with the WP.org update servers.