Sitemap Blank 2

My website is https://broadbandinternetprice.com/
I use Rank Math plugin to generate a sitemap.
It has been working fine, but recently, it fail to generate a sitemap and present a blank page when being visited.

URL:
https://https://broadbandinternetprice.com/sitemap_index.xml

I am currently using Cloudflare and Litespeed for my server.
I have tried disabling them to debug the issue but was out of luck.

I have also tried troubleshooting mode of the health check plugin.

I have also flushed the permalink.