The problem is the same as your other post: https://storejextensions.org/forum/view/10-jsitemap/7698-link-analyzer-answers-with-500-status-code-on-all-links.html

The crawler used for Links Analyzer and images sitemap is the same. Thus if the crawler test fails as in your case you have to investigate with your hosting provider to understand why it's blocked.

Of course ensure that there is not some third party extension installed on Joomla blocking the crawler.

I can't know the exact reason and i can't do anything on this matter because it's something related to the environment.

FAQ for already said common reasons: https://storejextensions.org/faq/my-images-sitemap-doesn-t-embed-all-images-in-my-site-what-could-be-the-problem.html

Best regards