Akeeba Backup for WordPress requires PHP 7.2.0 or later but your server only has PHP 7.1.33.Composer detected issues in your platform:

Your Composer dependencies require a PHP version ">= 7.2.5". 

<error>
    <code>internal_server_error</code>
    <title><![CDATA[WordPress &amp;rsaquo; Error]]></title>
    <message><![CDATA[&lt;p&gt;Ha habido un error crítico en esta web.&lt;/p&gt;&lt;p&gt;&lt;a href=&quot;https://wordpress.org/support/article/faq-troubleshooting/&quot;&gt;Aprende más sobre el diagnóstico de WordPress.&lt;/a&gt;&lt;/p&gt;]]></message>
    <data>
        <status>500</status>
    </data>
</error>