Hello,
Thank you for contacting us and sorry for any inconvenience that might have been caused due to that.
It seems like you purchased the plugin with some other email address.
Can you please share the email address which you used to purchase the plugin or you can search and forward the receipt from FastSpring.com so we can locate your account?
Meanwhile, please make sure you’ve selected the Organization for Person or Company otherwise the multiple locations option will not appear:

Let us know how it goes. Looking forward to helping you.
The thing is we forgot what the email we used to purchase Rank Math PRO, but we do have the username & password. Are you able to locate our account using only the username?
Hello,
Yes, we can do that. Please share the username here and we’ll locate your Rank Math PRO subscription.
Looking forward to helping 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.