Cviebrock sluggable not showing query results

I have installed the Cviebrock laravel sluggable plugin but I'm having issues querying my database now. I have the slug column and I can see the slug in the URL but it won't display anything from the search results as it was when I was using the category ID as a search term

Here is my category controller:

 public function show(Categories $slug)
    {
        $categoryMenu = Categories::all();
        $companies = Company::where('visable', 0)->get();
        $categories = Categories::all();
        $title = $slug->category;
        $products = Products::where('category_id', $slug->id)->get()->groupBy('company_id');
        $allCompanies = Products::where('category_id', $slug->id)->groupBy('company_id')->get();
        return view('allCategories')->with([
            'companies' => $companies,
            'allCompanies' => $allCompanies,
            'categories' => $categories,
            'products' => $products,
            'title' => $title,
            'categoryMenu' => $categoryMenu,
        ]);

And the category model:

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;
use Cviebrock\EloquentSluggable\Sluggable;

class Categories extends Model
{
    use Sluggable;

    /**
     * Return the sluggable configuration array for this model.
     *
     * @return array
     */
    public function sluggable()
    {
        return [
            'slug' => [
                'source' => 'category'
            ]
        ];
    }
    public function products()
    {
        return $this->hasMany('App\Products');
    }
}

and it's being passed in with:

<li class="nav-item">
    <a class="nav-link" href=""></a>
</li>

via Chebli Mohamed