Hello,
Thank you for reaching out to us. We’re sorry to hear about the issue you’re facing with activating Content AI Starter.
To activate Content AI in Elementor, please ensure that you have refreshed the credits after making the payment. You can do this by heading over to WordPress Dashboard → Rank Math → General Settings → Content AI and refreshing the credits. Here’s a screenshot for reference:

Once you’ve refreshed the credits, please go back to using Content AI in Elementor, and it should work without any issues.
If you need further assistance, please don’t hesitate to let us know.
Sources:
How to Use Content AI in Elementor » Rank Math
Content AI Overview » 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.