2checkout error upon returning to site after payment

I have just noticed that i'm getting missing orders in opencart and am only getting emails from 2checkout to say i have an order.
I'm using 2checkouts module for opencart
So when you go to pay for an order and fill in all the details like address etc thats all fine.
When you finish and click pay, when it redirects you to the callback url it gives me the error message

The response from 2checkout.com can't be parsed. Contact site administrator, please!

The url is
http://bluefoxy.co.uk/index.php?route=p ... t/callback

Apparently this is compatible with 1.5.6.4

I am using the extension provided by 2checkout themselves but all they have said is to reinstall opencart as it works elsewhere.. I tried that but it didn't work, I can't just delete the DB however as i have orders and customer details on there.

https://www.2checkout.com/shopping-cart/open-cart/

I have the settings on my 2checkout account setup fine as even 2checkout support has said so

would anyone be able to help at all?

Is there anyone that knows about this at all? 2checkout havnt fixed the issue.