Version 4.0.4 – cannot ping google, bing, about changes

The last ping to google etc about changes in the sitemap was a few days ago (successful).

I posted new content yesterday and today, and it did not ping google.

I can’t find a button to let manually ping either.

Question: How to force the plugin to ping google and bing about changes in the sitemap?

Besides the complaints from other people, google webmaster tools does accept the new format of the sitemaps of my blog and there is no loss in indexed pages!

https://wordpress.org/plugins/google-sitemap-generator/