I didn’t change the content, yet my SEO score changed
In Yoast SEO 10.0 we recalibrated the SEO analysis. This changed several assessments which may now give a slightly different SEO score for the same content. You can read all about the recalibrated analysis here: https://yoast.com/yoast-seo-10-0/.
Keep in mind that the SEO score will only be recalculated when the post or page is updated, with or without changing anything.