How to fix error "There was an error while retrieving the URL specified"

[cnway2010]

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

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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?

[XML-Sitemaps Support]

Hello,

please let me know your generator URL/login in private message to check this.

[cnway2010]

Hello,
I've sent message.
Best Regards
Pan