Sitemap error

I recently switched my website from squarespace to wordpress and at that time I also updated the url from a .com to a .co.nz. I now need to submit an xml sitemap through search console but when I added the Yoast SEO plugin and tried to retrieve my xml sitemap I got a 404 page error.

I then tried using xml-sitemaps.com and was going to upload the sitemap through my ftp server but also got a generic error message trying to generate the sitemap with that tool.

I currently have a Coming Soon page setup while I work on building my WP site and I am wondering if this is causing the issues. I am really stuck at this point and would appreciate the help with getting the sitemap sorted so the site can get indexed properly.