Question 1
I submitted the sitemap "sitemap_index.xml" to GWT.
Everything is fine but "post-sitemap.xml" which came up with an error.
The error message is:
General HTTP error: 404 not found
HTTP Error: 404
We encountered an error while trying to access your Sitemap. Please ensure your Sitemap follows our guidelines and can be accessed at the location you provided and then resubmit.
How do I fix this?
Question 2
I also have the plug in Google XML sitemap generator which generates a sitemap "sitemap.xml".
I have submitted this to GWT already previously. Does the "sitemap_index.xml" clash with this "sitemap.xml"?