Hello,
Thank you for contacting Rank Math and sorry for any inconvenience that might have been caused due to that.
Your account is already upgraded to the PRO version. You’ll also notice that the PRO badge is already showing on your account details.
We highly recommend going through the following guide to set up the plugin completely and correctly:
https://www.youtube.com/watch?v=cQLvCBVev3I
and
https://rankmath.com/kb/how-to-setup/
I hope that helps further.