Plugin did not work while changing themes

hi all,

i moved on from one theme to another and executed the plugin.

as per my understanding this plugin works great when different themes have different images sizes to be displayed in different ways.

in new theme plugin ran without any errors but the thumbnails sizes did not change at all.

am i missing anything here? kindly advise.

thanks

https://www.ads-software.com/plugins/force-regenerate-thumbnails/