Recently I have received a ticket from us user .

When he try to purchase any plan then this error shown.

Array
(
[TIMESTAMP] => 2016-09-17T16:49:36Z
[CORRELATIONID] => 7c57865816ced
[ACK] => Failure
[VERSION] => 72.0
[BUILD] => 25037053
[L_ERRORCODE0] => 10002
[L_SHORTMESSAGE0] => Security error
[L_LONGMESSAGE0] => Security header is not valid
[L_SEVERITYCODE0] => Error
)

Generally this error means you are not using the correct API credentials. If you are convinced your credentials are correct then take a look at your endpoint. Sandbox credentials will not be valid in the production environment and live credentials will produce this error in the sandbox.

Then i just login to WordPress Dashboard and check his paypal info so there was an empty space at the start or email and end of the email. Also there was empty space at the start of API Signature and at the end of API Signature.

I just remove that space and its working fine now.

Also you must need to fill complete form including.

• Thank you page - after successful payment
• Thank you page - after failed payment

Thanks for reading this article.