Error: 404 Not Found

Sorry, the requested URL 'http://u.limo/wp-admin/admin-ajax.php?channel_id=social_wechat&action=xh_social_channel&tab=login_redirect_to_authorization_uri&xh_social_channel=eae32193e9&notice_str=1295851415&hash=6f2dde09b49fd5bec772c4c01378d54f&redirect_to=https%3A%2F%2Fu.limo%2F1525%2F' caused an error:

Not found: '/wp-admin/admin-ajax.php'