Hi,
Try to activate the "always use direct call (UA)" setting. It should work better as sometimes, based on how you configure your checkout, and the payment methods you're using, the non direct call might not be taken into account by GA.
Otherwise, the javascript code is added on the thank you page, after your payment gateway redirects you back to the website after the payment if the direct call is not activated. If you turn on the debug option, you'll see the logging of the exchange with GA in the console of your web browser on that thank you page.
Also, please note that it usually takes 24h for GA to display the orders.