Hello,
Thank you for contacting the support, and sorry for any inconvenience that might have been caused due to that.
Do you mind if I ask if you happen to have a plugin “Font Awesome” installed on your website? We actually have had conflict issues lately with the FA plugin causing “Null” on the SEO Metabox.
If this is the case on your end, the folks from Font Awesome provided a quick fix for this. Please visit this support thread: https://wordpress.org/support/topic/plugin-conflicts-with-rankmath/
If this isn’t the case however, check if there are other plugins or your current theme that might be conflicting with Rank Math. You can determine that by following this guide: https://rankmath.com/kb/check-plugin-conflicts/
Here is a video you can follow as well: https://www.youtube.com/watch?v=FcIWRhcUP2c
Only the site admin would know and your users won’t be affected by this troubleshooting.
If the issue persists, please edit the first post on this ticket and include your WordPress login in the designated Sensitive Data section.
Please do take a complete backup of your website before sharing the information with us.

It is completely secure and only our support staff has access to that section. If you want, you can use the below plugin to generate a temporary login URL to your website and share that with us instead:
https://wordpress.org/plugins/temporary-login-without-password/
You can use the above plugin in conjunction with the WP Security Audit Log to monitor what changes our staff might make on your website (if any):
https://wordpress.org/plugins/wp-security-audit-log/
Please do take a complete backup of your website before sharing the information with us.
We really look forward to helping you.