Blocksy theme?
Seems to work for me.
Go to: https://playground.wordpress.net/?theme=blocksy&plugin=animations-for-blocks&url=%2Fwp-admin%2Fpost.php%3Fpost%3D2%26action%3Dedit
Paste this block (or add an animation to something yourself):
<!-- wp:paragraph {"animationsForBlocks":{"animation":"slide","variation":"up","duration":3000},"style":{"elements":{"link":{"color":{"text":"var:preset|color|palette-color-8"}}}},"backgroundColor":"palette-color-2","textColor":"palette-color-8","fontSize":"large"} -->
<p class="has-palette-color-8-color has-palette-color-2-background-color has-text-color has-background has-link-color has-large-font-size" data-aos="slide-up" data-aos-duration="3000">This is an example page. It's different from a blog post because it will stay in one place and will show up in your site navigation (in most themes). Most people start with an About page that introduces them to potential site visitors. It might say something like this:</p>
<!-- /wp:paragraph -->
Save, view page – slides up slowly.
You possibly have some CSS that overrides the transition-duration property. Inspect the element on your front end to find out if that’s the case and what’s causing it.
