Hello,
It is really weird and more if you disabled everything and it still doesn’t work.
We might need to take a closer look at the settings. Please edit the first post on this ticket and include your WP logins in the designated Sensitive Data section.

It is completely secure and only our support staff has access to that section. If you want, you can use the below plugin to generate a temporary login URL to your website and share that with us instead:
https://wordpress.org/plugins/temporary-login-without-password/
You can use the above plugin in conjunction with the WP Security Audit Log to monitor what changes our staff might make on your website (if any):
https://wordpress.org/plugins/wp-security-audit-log/
We really look forward to helping you.
I already did that. There is a link in there to a screenshot of the login I created for you.
Hi Keith,
It appears you had not enabled the page sitemap. And, you do not have any posts so there was nothing to show in the sitemap. That’s why you were getting a 404.
I have enabled the pages sitemap and now the sitemap is working fine.
Hope that helps and please do not hesitate to let us know if you need our assistance with anything else.
Thank you, Todd. Sorry, that was a silly oversite.
Hello Keith,
We are super happy that this resolved your issue. If you have any other questions in the future, know that we are here to help you.
If you don’t mind me asking, could you please leave us a review (if you haven’t already) on https://wordpress.org/support/plugin/seo-by-rank-math/reviews/#new-post about your overall experience with Rank Math? We appreciate your time and patience.
If you do have another question in the future, please feel free to create a new forum topic, and it will be our pleasure to assist you again.
Thank you.