When I create sitemap,there has an error as below:

There was an error while retrieving the URL specified: [ External links are visible to forum administrators only ]
HTTP Code:
HTTP/2 404
HTTP headers:
date: Fri, 31 May 2019 02:10:19 GMT
server: Apache
pragma: no-cache
cache-control: max-age=0, must-revalidate, no-cache, no-store
expires: Wed, 30 May 2018 02:55:17 GMT
x-content-type-options: nosniff
x-xss-protection: 1; mode=block
x-frame-options: SAMEORIGIN
set-cookie: X-Magento-Vary=e3cb9ab3566a693edff3edf
And my php version is 7.2.
How to fix this error?
I've sent message.
Best Regards