I bought, installed and configured Paypal API 2.3.11. In test mode when checkout I get this error:
SetExpressCheckout failed: Array ( [TIMESTAMP] => 2017-01-03T12:07:06Z [CORRELATIONID] => 197c3760b1042 [ACK] => Failure [VERSION] => 117.0 [BUILD] => 28387177 [L_ERRORCODE0] => 10002 [L_SHORTMESSAGE0] => Security error [L_LONGMESSAGE0] => Security header is not valid [L_SEVERITYCODE0] => Error )
Joomla: 3.6.5
JoomShopping: 4.15.1
PHP: 7.0.13
MySQL: 5.5.53
Website Url: http://www.terrafisch.ch
JoomShopping: 4.15.1
PHP: 7.0.13
MySQL: 5.5.53
Website Url: http://www.terrafisch.ch