Hello,
Thank you for contacting us and sorry for any inconvenience that might have been caused due to that.
Please make sure the Content AI module is enabled on your website from Rank Math > Dashboard > Modules:

If it is already enabled then please head over to your WordPress Dashboard > Rank Math > General Settings > Content AI and from there make sure the post type is selected:

If the issue still persists, then please try to follow this guideline for further troubleshooting: https://rankmath.com/kb/check-plugin-conflicts/
Let us know how it goes. Looking forward to helping you.
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.