minishop2 paypal checkout problem: Errorcode 10002

Hi,

I'm using MODX 2.5 together with minishop2-2.2.0-pl2 and I'm having the following problem:

I have one method for delivery and one for payment — paypal. Both are active.
When I press the checkout button an order is created but without going to paypal checkout just successful order message. And that's all.

I made the needed settings — you can see them in the attached files.

There is the following error log:

[2016-05-12 03:08:50] (ERROR @ /home/xxx/public_html/subdomain/core/components/minishop2/custom/payment/paypal.class.php : 67) [miniShop2] Payment error while request. Request: Array
(
    [METHOD] => SetExpressCheckout
    [PAYMENTREQUEST_0_CURRENCYCODE] => USD
    [PAYMENTREQUEST_0_ITEMAMT] => 0.1
    [PAYMENTREQUEST_0_SHIPPINGAMT] => 0
    [PAYMENTREQUEST_0_AMT] => 0.1
    [RETURNURL] => http://subdomain.site.com/assets/components/minishop2/payment/paypal.php?action=success
    [CANCELURL] => http://subdomain.site.com/assets/components/minishop2/payment/paypal.php?action=cancel
    [PAYMENTREQUEST_0_INVNUM] => 11
    [L_PAYMENTREQUEST_0_NAME0] => JD
    [L_PAYMENTREQUEST_0_AMT0] => 0.1
    [L_PAYMENTREQUEST_0_QTY0] => 1
)
, response: Array
(
    [TIMESTAMP] => 2016-05-12T07:08:50Z
    [CORRELATIONID] => 8ac3cf0e3fc76
    [ACK] => Failure
    [VERSION] => 74.0
    [BUILD] => 000000
    [L_ERRORCODE0] => 10002
    [L_SHORTMESSAGE0] => Security error
    [L_LONGMESSAGE0] => Security header is not valid
    [L_SEVERITYCODE0] => Error
)

Any suggestions?

Edit:
I checked the Errorcode 10002 and it says the credentials may be wrong. Will enter them again and write if the problem is solved.