Known issue (and solution) with setting USPS Carrier to Parcel
An issue was discovered in PowerStore 2.0, where using USPS Shipping and setting the Carrier to Parcel will cause an error in the shipping and the confirm.php page will redirect to the checkout_failure.php page.
We are now offering a very simple fix (just a file replacement) in the Download Center of our website. Log in and visit downloadcenter.php. Click on PowerStore; then click on the Known Issues section. Download the zip file and follow the instructions in the readme file.