Hello,
Thank you for contacting us and sorry for any inconvenience that might have been caused due to that.
We’ve checked from our end and we can also replicate the issue with the HTML sitemap.
We already escalated this issue to our development team and they are working on investigating this further. We will let you know as soon as possible when we have an update.
We really appreciate your kind patience regarding this matter.
Meanwhile, please don’t hesitate to contact us anytime if you have other questions to assist you further.
Thank you.
Hello,
We released a quick Beta update you can try to see if that helps.
Please enable the Beta update by following this:
https://rankmath.com/kb/version-control/#beta-updates

If you are unable to see an update, please clear Rank Math’s transients from:
WP Dashboard > Rank Math > Status & Tools > Database Tools > Remove Rank Math Transients > Remove transients

Please clear the caches, server, and WordPress after updating.
You can disable the Beta updates once you update to the latest version and if the issue is fixed.
We are here to assist. Thank you.
Hello,
Since we did not hear back from you for 15 days, we are assuming that you found the solution. We are closing this support ticket.
If you still need assistance or any other help, please feel free to open a new support ticket, and we will be more than happy to assist.
Thank you.