Is Google Search Console failing to retrieve your website’s sitemap? It is possible that you need to refresh your permalinks.
To do that:
- Go to your /wp-admin page.
- Go to the “Settings” menu and click on Permalinks.
- Once on the permalinks page, without altering anything, click on “Save Changes.”
Give it some time and then go test yoursite.com/sitemap.xml and see if Google is finally picking something up.
You can find some more ideas here:
So there you are staring at your WordPress site or admin page wondering what just happened. “This is going to auto-update in just a minute and all will be back to normal,” you tell yourself, but nothing happens. Well, I suppose it is time for the quickest fix of all times for a problem of this size.
It turns out that this is a classic of WordPress since Version 2.7. During an automatic update of your WordPress site, WordPress places a file named .maintenance in your blog base folder. For as long as that file will be there, visitors to your site will see the message “Briefly unavailable for scheduled maintenance. Check back in a minute.”
To bring your site back to usual business, just delete the .maintenance file either by FTP into the the folder that contains the wp-admin folder or by way of your hosting site.
Before I let you go, let me tell you about some people who have gotten really mad over this issue. They could not find the .maintenance folder because the file is actually hidden from Linux/Unix users since it starts with a dot. So, please make sure your set your File Manager or FTP client to show you hidden files. You can read the discussions here and here. Some of them address the question of where the file is actually located.
Important: Please remember verify that the update has been completed. Otherwise, try again.
That’s it for now, folks!
Source: The Maintenance FAQ at Codex.WordPress.org