The plugin stopped working

Is there a way to keep my system animation effects off, and still have the animation in the browser working?

Yes, you would need to add this custom code (to your child theme’s functions.php, a mu-plugin, snippet, etc):

add_action('wp_enqueue_scripts', function() {
	if(defined('WSD_ANFB_AOS_HANDLE') && wp_style_is(WSD_ANFB_AOS_HANDLE, 'enqueued')) {
		// Override 'screen and (prefers-reduced-motion: no-preference)'
		wp_styles()->registered[WSD_ANFB_AOS_HANDLE]->args = 'screen';
	}
});

The animations on your test site work for me, so you also probably have prefers reduced motion enabled on your computer.

I’m not sure why the snippet isn’t having an effect for you though.

But it’s recommended to turn prefers-reduced-motion setting off rather than use the snippet – ask an AI how to do it, it will give you different places to check, depending on your OS and browser. It could also be enabled in Chrome dev tools: https://i.imgur.com/SpnclNP.png

Add this snippet to a Custom HTML block on any page, it will tell you whether the setting is on or off:

<style>
.test-notice {
	padding: 1rem;
	margin-block: 1rem;
	color: white;
	border-radius: 4px;
	display: none;
}
@media (prefers-reduced-motion: reduce) {
	.test-notice[data-enabled=true] {
		display: block;
		background-color: red;
	}
}
@media (prefers-reduced-motion: no-preference) {
	.test-notice[data-enabled=false] {
		display: block;
		background-color: green;
	}
}
</style>
<div class="test-notice" data-enabled="true">Reduced motion is enabled, animations won't play.</div>
<div class="test-notice" data-enabled="false">Reduced motion is not enabled, animations will play.</div>

Here’s another PHP snippet (for child theme’s functions.php) that can change the plugin’s default behavior though:

add_action('init', function() {
	if(defined('WSD_ANFB_AOS_HANDLE')) {
		wp_deregister_style(WSD_ANFB_AOS_HANDLE);
		wp_register_style(
			WSD_ANFB_AOS_HANDLE,
			plugins_url('build/aos.css', WSD_ANFB_FILE),
			[],
			WSD_ANFB_VER,
			'screen' // Override 'screen and (prefers-reduced-motion: no-preference)'
		);
	}
}, 11);