Hello,
Thank you for reaching out to us. We apologize for the inconvenience you are facing with the Rank Math AI tools.
It seems that you have the required credits for using the AI tools, but there might be a need to refresh the credits to start using Content AI. Please head over to your WordPress Dashboard → Rank Math → General Settings → Content AI and refresh the credits. Here’s a screenshot for reference:

After refreshing the credits, please try using the AI tools again, and it should work without any issues.
If you encounter any further issues, please feel free to let us know, and we will be happy to assist you further.
Sources:
Content AI – Your Personal AI Assistant by Rank Math
Content AI Credits and Plans: Everything You Need to Know » Rank Math
This is an automated reply from Rank Math Support Bot. If you need further assistance, please reply to this topic and a human support agent will reply to you shortly.
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.