Hi,

the problem is not directly related to the sitemap generated by JSitemapPro otherwise some errors would have been reported.

There are few things that you can try to understand something more:

1. Submit a new sitemap link to force Google Webmasters to fetch a new sitemap, for example index.php?option=com_jmap&view=sitemap&format=xml&v=2

2. Check if GoogleBot is allowed to access your website and server

3. Check if you have some extensions or plugins for SEF links, etc that could manage some redirects or blocks for GoogleBot such as Admin Tools

4. Ensure that links included in the sitemap are all valid and reachable

Best regards
John