Default category image setting is not working

Hi I am using this plugin and found one option “Default category image setting”. I set the value “Replace articles with no image with default category image” for this option. Which supposed to show the category image for articles that don’t have any image. But it’s not working.

I am using the default twentyforteen theme and showing feeds by activating “Feeds to Post”.

Am I doing anything wrong?

Please help.

https://ww.wp.xz.cn/plugins/wp-rss-multi-importer/