@morkovka52
We understand that you can’t purchase the plugin at the moment and would still like to get more help on the issue.
Certainly, as support agent @mazedulislamkhan explained earlier that even though the Yoast SEO snippet preview isn’t showing the value of the relevant template variable, you should still see the relevant template variable’s output on the front end part of the website. So, search engines won’t have any issues finding the right title for the relevant page.
So right now since the issue seems only on the backend where the variable doesn’t output the value on the Yoast SEO preview, it is still outputting value on the source code (front page) where Google can read this. It won’t affect your site SEO nor the Yoast SEO analysis.
Having said that, 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.