Blank Sitemap 5.3.3.1

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This may have been posted beofre but I am struggling.

I was running concrete 5.2 but the sitemap went blank. I then upgraded to 5.3.3.1 but the sitemap is still blank.

I have renamed the config.php page, and re-installed in to a new database but I am getting the same problem.

I have cleared the cache, checked permissions but still no luck!

Any suggestions are gratefully appreciated!