Paypal adaptive payments

-- HikaShop version -- :2.3.1
--Hikamarket Version --:1.4.1
-- Joomla version -- : 3.2

Hi,

I am trying to set up paypal adaptive payments in a sandbox environment. I have acquired the relevant details:
username
password
signiture
APP id

I have put the App id in the Application ID area of the plugin and when I try to make a test purchase I get this error:

The X-PAYPAL-APPLICATION-ID header contains an invalid value

if I take out the Application ID and leave it blank I get this error message:

Authentication failed. API credentials are incorrect.

Would anyone happen to have had the same problem and if so could you please tell me what I might be doing wrong?

Many thanks in advance for your help!

Hi Jerome - thanks for your fast reply.

I have tried in debug mode and still get the same error.

Here are a couple of screen shots...it is probably something I am doing wrong - as I am still trying figure out hikashop and hikamarket

Thanks again for any help