Regenerate slugs that have been created already

So, I created a few pages and renamed them with the plugin and it was perfect, and then I started working on one of the pages. I decided instead of designing the other pages from scratch, I just decided to clone the designed page and just redo the slugs on the cloned pages. I deleted the old pages and I went into the plugin settings and deleted the permalinks from there so that I can rename the new cloned pages with the pages I named in the beginning. But, it won’t work. And I think it’s because I technically already named other pages with that slug. But I deleted the old pages with the slug, so I don’t know why it won’t work anymore. Every time I delete the plug and regenerate it with the new one, it jumps back to a default slug.