While you should never see this error, it has happened from time to time, so we want to provide a found work-around if you run into it:
Once you turn off Test Mode, if you or your customers receive the message at checkout of "Payee Not Consented", this means that the Payee (you, the seller) does not have appropriate consent to allow the API caller to process this type of transaction on their behalf. Your current setup requires the 'payee' to provide a consent before this transaction can be processed successfully.
This happens when, for some reason, the permissions you granted us did not take effect within normal login flow.
The fix is to manually grant permissions to a third party:
Click on this link: https://www.paypal.com/cgi-bin/webscr?cmd=_profile-api-grant-authorization
Enter : paypal_api1.payableplugins.com
Select all permissions up to and including "Dynamically encrypt PayPal buttons on your web site", and lastly "Use Express Checkout to process mobile payments"
This should eliminate the permission issue and allow your customers to pay.