Stuck on a tricky Laravel debugging issue, need help!

I'm building a very simple inventory management app, mostly to learn the ropes of Laravel development and get familiar with Eloquent. Everything was going smoothly until I decided to refactor some of my model relationships. Specifically, I changed a hasMany relationship to a belongsToMany between Product and Category models, thinking it would be more flexible for products belonging to multiple categories.

Now, when I try to fetch products along with their categories, I'm getting an error. I expect to see a product with a collection of its associated categories, but instead, the application crashes.

I've tried quite a few things already, trying to follow what I've learned from tutorials:

• Checked the Laravel logs (storage/logs/laravel.log) for any obvious errors.
• Cleared all caches (php artisan cache:clear, php artisan config:clear, php artisan view:clear, php artisan route:clear).
• Run composer dump-autoload to regenerate the autoloader.
• Used dd() in various places to inspect the data before the error occurs, which helped me narrow down the exact line but not the root cause.
• Searched extensively on Stack Overflow and various Laravel forums for similar issues, but nothing quite matches my specific scenario or solution.

The specific error I'm encountering is a BadMethodCallException. It seems like it's trying to call a method that doesn't exist on the Product model, even though I've defined the categories() relationship.

Here's a snippet from my Laravel log showing the error:

[2023-10-27 10:35:01] local.ERROR: BadMethodCallException: Call to undefined method App\Models\Product::categories() in /var/www/html/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Relations/Relation.php on line 301
Stack trace:
#0 /var/www/html/app/Http/Controllers/ProductController.php(45): Illuminate\Database\Eloquent\Relations\Relation::__callStatic('categories', Array)
#1 [internal function]: App\Http\Controllers\ProductController->index()
#2 ...

And in my Product model, I have this relationship defined:

// app/Models/Product.php
namespace App\Models;

use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Factories\HasFactory;

class Product extends Model
{
    use HasFactory;

    public function categories()
    {
        return $this->belongsToMany(Category::class, 'product_category', 'product_id', 'category_id');
    }
}

The controller code that triggers this is quite simple:

// app/Http/Controllers/ProductController.php
public function index()
{
    $products = Product::with('categories')->get(); // This line throws the error
    return view('products.index', compact('products'));
}

I'm at a loss here. As a newbie to Laravel development, I'm not sure if I'm missing something fundamental about belongsToMany relationships, or if there's some caching I'm not aware of that's causing this old method call to persist. Could it be a namespace issue, even though I've checked them multiple times?

Any pointers on where to look next, common pitfalls for this specific BadMethodCallException with relationships, or general Laravel debugging strategies for beginners would be incredibly helpful.

Thanks a lot in advance for your time and help! Waiting for an expert reply.