Hello,
Thanks for contacting us, and sorry for any inconvenience that might have been caused due to that.
Please head over to WordPress Dashboard > Settings > General and make sure there are no mismatches in the WordPress URL and Site URL in those options.

If you have different website URLs in there, that would explain the error message as they need to match for the connection to happen correctly.
After that, please try disconnect and reconnecting your Rank Math account again to see if this resolves your issue.
If the issue still persists, you can try adding the following filter on your website and then reconnect to your account.
/**
* Filter whether we need to check for URL mismatch or not.
*/
add_filter( 'rank_math/registration/do_url_check', '__return_false' );
After that, the plugin should be able to stay connected without any issues.
Here is a guide you can follow to add the filter:
https://rankmath.com/kb/wordpress-hooks-actions-filters/
Let us know how it goes. Looking forward to helping you.
Thank you.
Hello,
We are super happy that this resolved your issue. If you have any other questions in the future, know that we are here to help you.
If you don’t mind me asking, could you please leave us a review (if you haven’t already) on https://wordpress.org/support/plugin/seo-by-rank-math/reviews/#new-post about your overall experience with Rank Math? We appreciate your time and patience.
If you do have another question in the future, please feel free to create a new forum topic, and it will be our pleasure to assist you again.
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.