我尝试更新数据库中的字段，但收到此错误

"{"error":"Resource item not found."}"

下面是我的更新代码

public function update(Request $request, $merchant_id)
    {
        // Validation for required fields (and using some regex to validate our numeric value)
        $request->validate([
            'fees'=>'required',
    
        ]); 
        $merchants = Merchants_data::find($merchant_id);
        $merchants->fees =  $request->get('fees');
        $merchants->save();
 
        return redirect('/manage_merchants')->with('success', 'Transaction Fee updated.'); // -> resources/views/stocks/index.blade.php
    }

下面是我的路线

Route::patch('update_merchant/{merchant_id}', 'MerchantsController@update')->name('update');