Having trouble getting the PayPal system to work. Got a code, have a test email account, setup whatever I could find in PayPal.
Getting a “Security header is not valid”.
If I take it of Test mode, then the access to PayPal is successful, but my client says they are unable to complete a payment. Disregard for now until I can figure it out.
There are already several topics regarding the Security header is not valid error. Please take a look at them:
https://community2.invoiceplane.com/t/error-security-header-is-not-valid/945
https://community2.invoiceplane.com/t/topic/1197