Problem with custom Joomla plugin (events usage)

Question

I tried everything I could (yes, searching with google for a long time too) but I can't find what I am doing wrong here. I am trying to write Joomla plugin to change shortcode into list od adverts on OtoMoto.pl. But I am stuck on changing shortcode to any text. For some reason joomla don't even trigger my code in function. Could anyone help me with that? I am using Joomla 3.9.23 Stable, PHP 7.4.10 and below is my code:
otomoto.php:

<?php
defined( '_JEXEC' ) or die( 'Restricted access' );
class plgContentOtoMotoShortcode extends JPlugin
{
    protected $autoloadLanguage = true;

    function onContentPrepare($context, &$article, &$params, $limitstart = 0)
    {
        var_dump($article);
        $list_of_adverts = "Temporary";
        $text = str_replace('[otomoto]', $list_of_adverts, $article->text);
        $article->text = $text;
        return true;
    }
}

otomoto.xml

<?xml version="1.0" encoding="utf-8" ?>
<extension version="3.2" type="plugin" group="content" method="upgrade">
    <name>otomoto</name>
    <author>Futuristic Tomasz Burzyński</author>
    <creationDate>November 2020</creationDate>
    <copyright>Copyright (C) 2020</copyright>
    <license>Private, if you get this code for free you probably have it illegaly</license>
    <authorEmail>kontakt.futuristic@gmail.com</authorEmail>
    <authorUrl>https://futuristic.com.pl</authorUrl>
    <version>0.0.2</version>
    <description>Shortcode for OtoMoto adverts list</description>
    <files>
        <filename plugin="otomoto">otomoto.php</filename>
        <filename>index.html</filename>
    </files>
    <config>
    </config>
</extension>

Instalation of plugin went without problems so I really have no idea what is going wrong. I will add one more thing: I checked, plugin code is loaded on site, but its event just doesn`t work. I will be gratefull for any tip what's wrong with that code.

Answer 1

It's not triggering because the class is incorrect.

The class of the plugin must correspond to the plugin="" attribute value on the <filename> element in your XML file. It's also case sensitive.

Seeing as you have used:

<filename plugin="otomoto">

you should replace:

class plgContentOtoMotoShortcode 

with:

class plgContentOtomoto