Sitemap is empty

I hope you are doing well!
I have a SEO question relating specifically to the sitemap.
My sitemap is empty and contains no link. I had the auto-generated sitemap on and it was empty. I tried having a custom xml sitemap and turned off the auto-generated sitemap off, but still the sitemap of my website is empty. Any idea why this might be the case and how I can solve this?

Link to the sitemap:

Works when I run it through a free crawler here: