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When Tried To Process Paypal Checkout Express, 'Errors: 1000x: Security header is not valid' Prompts

Synopsis:

When tried to process Paypal Checkout Express, this message is displayed  'There is a problem posting to Paypal Express Checkout. Here are some details about the problem: resp.Ack: Failure| resp. Errors: 1000x: Security header is not valid'' 

Solution:

Please check your Paypal Checkout Express if it is set to SANDBOX MODE instead of LIVE MODE.


API Error Codes

https://developer.paypal.com/webapps/developer/docs/classic/api/errorcodes/

These are the possible causes:
1. You have your PayPal module configured to Sandbox but have not used Sandbox API credentials.
2. You have your PayPal module configured to Live but have not used Live API credentials.
3. You have mistyped one or more API credentials entries, including but not limited to leaving trailing spaces.
4. You have deleted and/or recreated new API credentials in your PayPal account but have not copied those new credentials back to your store.


Applicable Versions:

All Connected Business Version


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