Cannot install 'Responsive Add Ons'

I have just installed responsive v1.9.7.7 and following the instructions attempted to install the recommended plugins. I ran into two problems:

(1) The bulk installation process fails with blank page, no error message. As a work-around, I installed the several plugins individually using the WP plugin installer.

(2) The plugin called ‘Responsive Add Ons’ will not install. It returns an error:

object(WP_Error)#422 (2) { ["errors"]=> array(1) { ["plugins_api_failed"]=> array(1) { [0]=> string(219) "An unexpected error occurred. Something may be wrong with ww.wp.xz.cn or this server’s configuration. If you continue to have problems, please try the support forums." } } ["error_data"]=> array(1) { ["plugins_api_failed"]=> string(2) "N;" } }
Something went wrong with the plugin API.

The plugin does not appear in a search at WP.org.

So, I will have to skip installing that one.