As so many users here I have suffered from "Page Not Found" error when I click on:
but I noticed that the error appears with plugin version 1.4.22 & 1.4.23
When I downgrade to version 1.4.21 all things go very well !!!!
To downgrade proceed as follows:
1. from plungin page click on the tab "Developer" and download the vesion 1.4.21
or download directly from here
2. go to admin panel and select "import and export" then select "Export Settings" & a file named "settings.zip" will be downloaded to you.
3. Deactivate the plugin from admin panel.
4. Delete the plugin from admin panel also.
5. select Add New Plugin and select upload then upload the .zip file you have downloaded for version 1.4.21
6. Activate the plugin then select import settings and upload the file "settings.zip" that you have downloaded in setp 2.
Now test yoursite.com/sitemap-index.xml ....!!!
I don't know why version 1.4.21 is the most stable version relating sitemap
Does anyone knows ????