Hello,
Thank you for contacting us and sorry for any inconvenience that might have been caused due to that.
Please follow these steps:
A. Pre-check List
1. You should not be using any other Google Analytics plugin.
2. Update to the latest versions of Rank Math Free & PRO
3. Ensure that you are logged in to your account:

4. Disconnect and reconnect your account from inside WordPress:

B. Refresh Tokens
1. Please delete RankMath’s app from here:
https://myaccount.google.com/permissions

2. Re-create tables by clicking WP Dashboard > Rank Math > Status & Tools > Database Tools and click the Re-create database Table
button.

3. Reconnect the account inside Rank Math by clicking here and ensure that you approve all the permission notices that show up:
Please make sure that you’ve connected the correct Google account and not connecting to Google Search Console via a domain property but rather a URL prefix and that you have verified the correct version of your website on the Google Search Console (HTTP or HTTPS, www or non-www).
After that, please try reconnecting your Google Account again from WordPress Dashboard > Rank Math > General Settings > Analytics, and don’t forget to check all the necessary permission.

If the settings are not getting saved properly, please try saving the settings for the Analytics with a different browser such as Google Chrome. If you’re already using Chrome, then you can try it in Incognito mode just to save the settings.
Allow all the permissions on the next screen.

4. Let the process complete, which might take around 30 minutes.
5. Now head over to WP Dashboard > Rank Math > Status & Tools > Database Tools and click the Rebuild Index for Analytics
button.

6. Please check if the data shows up here:
/wp-admin/admin.php?page=rank-math-analytics#/

If that does not help, please paste the data from here:
WP Dashboard > Rank Math > Status & Tools > System Status and click the Copy System Info to Clipboard
button

You can also use tools like imgur for screenshots or loom for screencasts to record the process and share the generated links here.
Let us know how that goes. Looking forward to helping you.
Thank you.