My sitemap issue appears to have been resolved. Got a message from Google in my GWT account…
“Index coverage issues successfully fixed for site.”
Issue: I have been using the ‘Google XML Sitemaps’ plugin for many months prior to my recent sitemap issue. Went to GWT and did a ‘Fetch as Google’ and the Downloaded HTTP response appeared that showed a sitemap issue — no urls appeared.
Note: Just do a Fetch, not Fetch and Render
Solution: Deactivated the ‘Google XML Sitemaps’ plugin and replaced it with ‘Google Sitemap by BestWebSoft’. Did another ‘Fetch as Google’ and behold…
All my website’s urls appeared in the Downloaded HTTP response window. Also, the one sitemap issue that disappeared under Sitemaps in the GWT disappeared as well.
I am not using the Yoast SEO plugin but a different SEO plugiinstead. I would think that if you can disable the sitemap in Yoast and use the ‘Google Sitemap by BestWebSoft’ plugin instead, your issue will get resolved. In that case, the issue would appear to be with the Yoast sitemap and other sitemap plugins.