ActiveMerchant throws an invalid transaction error

I am trying to incorporate ExpressCheckout with Paypal using Active
Merchant and when I click on the express checkout button it takes me to
the paypal site and gives me an error that says Invalid transaction
error please use the ......

I notice that the error log does not generate a token at the time of
sending the request and it looks something like this

https://www.paypal.com/cgibin/webscr?cmd=_express-checkout&token=

So i feel that the error lies there but I may be wrong.

I have a setup a paypal account and a buyer seller accounts are in
place.

My Controller looks like this

def express
    cart = find_cart
    price = cart.get_price_in_cents
    response= EXPRESS_GATEWAY.setup_purchase(price,
{:ip=>request.remote_ip, :return_url=>new_orders_url,
:cancel_return_url=>"http://localhost:3000/search/home"})
    redirect_to EXPRESS_GATEWAY.redirect_url_for(response.token)
  end

I would appreciate any kind of help with this.

Thanks