Meta Description issue

I am using this plugin on my site.
I’m having trouble setting the [Meta Description] of the article.
I have set it on the setting screen of this plug-in, but the setting is not reflected depending on the article. Some articles are reflected in the search results, but the [Meta Description] display of most articles is an excerpt of the article.
I have already taken measures against suspicious plugins and settings.
Does anyone know what the cause is?
I look forward to working with you.