Hello,
Thank you for contacting Rank Math, and sorry for any inconvenience caused.
I logged in to your website and created a draft post and added a meta description and focus keyword to the post, it looks like access to this file is getting blocked:
/wp-json/rankmath/v1/updateMeta?_locale=user

If you are using Cloudflare or any security plugin, you should whitelist the file in Cloudflare and Firewall, if that does not help I would recommend contacting your hosting support, to check if something is blocking access to that file.
Here is a guide you can follow to fix this issue:
https://rankmath.com/kb/meta-data-not-saving/
I hope this helps. Looking forward to helping you.
Thank you. Whitelisting the updateMeta? path on the host’s firewall allowed me to save SEO data.
Grace
Hello,
We are super happy that your issue is resolved. 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.