I generated my sitemap and saved it as an XML file. When I submitted the sitemap to Google, I got the following error message:
Unsupported file format
Your Sitemap does not appear to be in a supported format. Please ensure it meets our Sitemap guidelines and resubmit.
Thanks for you help,
Dianne

That file you have is not a sitemap for google, it’s a project file saved as xml.
Under the sitemap tab, choose the export tab, then Sitemap XML to create a google sitemap.
That will do the job.
Best regards,
Jim.