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I used paypal express and occur Security header is not valid top top urgent


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I input all the necessary information on the paypal express checkout of payment modules under administration panel as follows.

And then I got to the catalog site, click the product and click the 'check with out paypal' icon. It occurs an error with

red highlight 'Security header is not valid'. Please please help. Many thanks!


PayPal Express Checkout

Enable PayPal Express Checkout

Do you want to accept PayPal Express Checkout payments?





API Username







API Signature:Tx7ye2OksokJICKDJLSKJ-OI-CJKJSLajd-ubiJICI2



Transaction Server



Transaction Method






Payment Zone

--none--CaliforniaFloridaHawaiiHong KongWashington


Set Order Status



Sort order of display.




cURL Program Location


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..... It occurs an error with

red highlight 'Security header is not valid'. Please please help. Many thanks!....


Get the same thing and am getting quite annoyed with it. It's supposed to be caused by entering the wrong usernam/password etc but I have trippelchecked, it IS correct. So..... what's causing this?





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API Username

xyz_api1.hot.com //this appears wrong.



API Password: 65HUH*******ZKD



API Signature:Tx7ye2Ok*******CJKJSLajd-ubiJICI2



one of these three values are wrong or YOu trying sandbox by placing live paypal values or vice versa.

Ask/Skype for Free osCommerce value addon/SEO suggestion tips for your site.


Check My About US For who am I and what My company does.

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  • 2 weeks later...

i experienced the same problem, but after inputting the API password, signatures etc again everything works! Hope it solves your problems too.

Edited by OllieA
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  • 2 months later...

I was having the same problems...

First internal server error.. turned out to be Curl wasn't installed on my hostgator account.


Then the invalid security errors..


Turned out to be I had it in sandbox with live api sigs and data...


Works now!


Thanks everyone..

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  • 3 years later...
  • 2 months later...

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