Custom CSS in Totara

Hi,

i really like H5P and i would to change the css for our own style. We are using Totara and i tried to follow this guide: https://h5p.org/documentation/for-developers/visual-changes
The thing is i dont see any changes in Style.

In our theme i use the following renderers.php:

<?php

require_once($CFG->dirroot . '/mod/hvp/renderer.php');


class theme_ventura_mod_hvp_renderer extends mod_hvp_renderer {

// H5P Custom CSS	
	    public function hvp_alter_styles(&$styles, $libraries, $embedType) {
        global $CFG;
        if (
            isset($libraries['H5P.InteractiveVideo']) &&
            $libraries['H5P.InteractiveVideo']['majorVersion'] == '1'
        ) {
            $styles[] = (object) array(
                'path'    => $CFG->httpswwwroot . '/theme/ventura/style/custom.css',
                'version' => '?ver=0.0.1',
            );
        }
    }
	
}

And i want to change the button style:

.h5p-joubelui-button {
	background: black;
}

Can someone help me with that? What am i doing wrong?

Best regards
Manuel