Hi,
Thanks a lot for your query and we are so sorry about the trouble this must have caused.
Could you please try now?
There could have been an issue when you tried.
Or, please open a new tab and login in via that tab. Then, head to this page and perform hard refresh:
https://rankmath.com/my-account/
Hard Referesh method:
Windows: Ctrl + F5
Mac/Apple: Apple + R or command + R
Linux: F5
Then, continue to connect/authorize your website in the tab where your website is open.
Hope that helps and please do not hesitate to let us know if you need our assistance with anything else.