Paypal Gateway Error

i try use gateways paypal ,but it always error :
Paypal Gateway Error:
Array
(
[TIMESTAMP] => 2016-09-07T17:22:05Z
[CORRELATIONID] => ab14bcbdc865b
[ACK] => Failure
[VERSION] => 117.00
[BUILD] => 24765677
[L_ERRORCODE0] => 10002
[L_SHORTMESSAGE0] => Security error
[L_LONGMESSAGE0] => Security header is not valid
[L_SEVERITYCODE0] => Error
)

Help me.and how use payment woocome for lms?