What is the issue?
This means that an XML file on your page is broken with a status code 4xx or 5xx. The Sitemap.xml is a typical example of an XML file on your page. If your page has a broken XML file, the page will not be displayed correctly. If your Sitemap.xml is one of these broken files, search engines bots will not analyze your page as you've specified.
How to fix
To fix this issue, check all mentions to the XML file and ensure that the link is correct.
The columns "incoming links" and "incoming references" show how many pages link to the broken file.
Click on either of these columns, and a new window will open, where you see a complete list of the pages containing the link to the broken XML file.
Look at the column "anchor text" to find where the link is on the page. Or, open the reference in your browser, right-click, and view the page source, where you can copy and paste the broken file link into the find function to see where the link is.
Then either you or your developer can change the link in the source code.
Learn more about this here.