Learn2 Theme: prev/next not working

{% extends 'partials/base.html.twig' %}
{% set tags = page.taxonomy.tag %}

{% if tags %}

    {% set progress = page.collection({'items':{'@taxonomy':{'category': 'docs', 'tag': tags}},'order': {'by': 'default', 'dir': 'asc'}}) %}
{% else %}
    {% set progress = page.collection({'items':{'@taxonomy':{'category': 'docs'}},'order': {'by': 'default', 'dir': 'asc'}}) %}
{% endif %}

{% block navigation %}
    <div id="navigation">
    {% if not progress.isFirst(page.path) %}
        <a class="nav nav-prev" href="{{ progress.nextSibling(page.path).url }}"> <i class="fa fa-chevron-left"></i></a>
    {% endif %} 

    {% if not progress.isLast(page.path) %}
        <a class="nav nav-next" href="{{ progress.prevSibling(page.path).url }}"><i class="fa fa-chevron-right"></i></a>
    {% endif %}
    </div>
{% endblock %}

{% block content %}
    {% include 'partials/page.html.twig' %}
{% endblock %}

taxonomy:
    category:
        - docs