You are using a “Classic Paragraph” block which is a block created by a 3rd party plugin, possibly TinyMCE Advanced.
I tested the TinyMCE Advanced plugin and it detected internal and outbound links. This could mean that you’re either using another plugin that creates the classic block or there is a conflict between plugins/theme.
Just to be sure, we would like to rule out any plugin or theme conflicts that may occur. The fastest way to do this is to?deactivate all non-Yoast plugins and switch to a standard theme?like?Twenty Nineteen.?
Test this on your development or staging site, if you have one. If not, we recommend using the?Health Check & Troubleshooting?plugin. This plugin allows you to run a conflict check?without affecting normal visitors to your site.
As we can imagine that you’re unfamiliar with checking for conflicts, we’d like to point you to a step-by-step guide that will walk you through the process:?How to check for plugin conflicts.