When using CiviCRM 4.6.4, we notice when adding a $0 (Free) item to a price set, and a user contributes, they are asked to confirm, but then get this error with our Paypal Website Payment Pro processor:
Payment Processor Error message: 10525: Invalid Data This transaction cannot be processed. The amount to be charged is zero.
When someone chooses a $0 amount, no Paypal payment method is presented on the form, yet it still seems to opt-in to using that processor. We have no other payment processors enabled.
How do we fix?
We also notice that when using CiviDiscount,if we make a 100% off CODE for a membership, it is also rejected by Paypal with the above error.