Thanks for contacting us, and sorry for any inconvenience that might have been caused due to that.
Assuming you are using the latest version of all the plugins and the themes (please update if not yet), it would seem like a conflict with one of the plugins or the theme you are using.
Only the site admin would know and your users won’t be affected by this troubleshooting.
If the issue persists, please record a video screencast using a tool like Loom showing the troubleshooting and edit the first post on this ticket and include your WordPress & FTP logins 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:
Apologies for the delay as this ticket seems to have been stuck in our drafts section for some reason.
I’ve checked your site, and your WordFence is not blocking Rank Math’s saving module.
In this case, please get in touch with your web host and ensure that the ModSecurity (ModSec) is disabled or they are not blocking any process of the plugin.
You can also ask them to whitelist Rank Math’s routes for saving: