Error Message 10002: Security header is not valid

[jennylcr]

I'm trying to make transactions by using a paypal pro account, however, it keeps giving me the same error. I have the credentials checked several times, the code is working for other paypal accounts, but no luck on this one. If someone can take a look, that would be helpful.

Here is the response message:

{"TIMESTAMP":"2018-02-28T22:07:53Z","CORRELATIONID":"b2ef63f12871a","ACK":"Failure","VERSION":"119.0","BUILD":"39949200","L_ERRORCODE0":"10002","L_SHORTMESSAGE0":"Security error","L_LONGMESSAGE0":"Security header is not valid","L_SEVERITYCODE0":"Error"}

Username: <removed>

[Snow-Cat]

You may want to visit the Merchant Support Community as there are other developers and PayPal Techs there who may be able to help.