When a customer tries to pay for a sale using PayPal checkout in Magento they are not able to complete their order, the error "Unable to process Express Checkout approval." appears. When you look at your logs you see this is caused by the error "Object of class Varien_Object could not be converted to int in" showing a particular line of code with "OnePica/AvaTax" in the details of the Stack Trace.
- This error is due to developer mode being enabled in your environment, disable developer mode to resolve
- Refer to your Magento user guide to determine how to disable developer mode for your particular store configuration