Hello,
Thank you for contacting Rank Math support, and sorry for any inconvenience that might have been caused due to that.
Please ensure that your sitemap module is enabled under Rank Math > Dashboard > Modules:

Then, the sitemap settings should appear under the Rank Math menu:

If you are referring to the actual sitemap page itself, you should be able to access it here:
https://yourdomain.com/sitemap_index.xml
If the sitemap is still missing, please share your website URL so we can further check it on our end.
Looking forward to helping you on this one.
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.