Hello,
Thank you for contacting the support and we regret the inconvenience caused.
It seems like you were able to make the purchase as the PRO subscription is already attached to your account.
Please follow this guide to install and activate Rank Math PRO on your website(s):
https://rankmath.com/kb/how-to-upgrade-to-rank-math-pro/
Hope this helps and please feel free to let us know if you require any assistance.
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.