I installed 7.x-2.3 a couple of days ago.
During cron run - watchdog reports: 'Submitted the sitemap to http://www.google.com/webmasters/tools/ping?sitemap=https://xxx.org/site... and received response 200'
The output of https://xxx.org/sitemap.xml when viewed in a browser works fine.
I can see a cached file in: /sites/default/files/xmlsitemap/NXhscRe0440PFpI5dSznEVgmauL25KojD7u4e9aZwOM/1.xml and manually uploading this from Google webmaster tools worked fine, so I'm not sure where the sitemap submitted by the site is going to, as I'm only seeing my manual one on the webmaster tool dashboard. The site is otherwise being crawled OK.
I've set webmaster tool Properties to include www / non-www and https/http values with https://xxx.org being the preferred.