Laravel eloquent with() returns null

class Bid extends Model
{
    protected $table = "bid";

    protected $primaryKey = 'bid_id';

    protected $guarded = [];

    protected $with = ['services'];

    public function services() {
        return $this->hasMany(Service::class, 'bid_id');
    }

    public function area() {
        return $this->belongsTo(Area::class, 'area_id', 'area_id');
    }
}

class Area extends Model
{
    protected $table = "location_area";

    protected $primaryKey = 'area_id';

    protected $guarded = [];

    public function city()
    {
        return $this->belongsTo(City::class, 'city_id');
    }
}

When I am trying to access

Bid::with('area')->find(BID_ID);

It is returning Null

But if I am doing like:

$bid = Bid::find(BID_ID);
dd($bid->area);

It returns Area table values. What is going wrong? Please Help me. I am having this problem from a long time. Thank You in advance :)

via Chebli Mohamed