So... was working with a customer that was trying to checkout, when they submitted the order via the PP Express Checkout it redirected...with no errors or notices to paypal.com. After investigation it was found the card was being denied. So I went to PP and opened a ticked after a few phone conversations.
This is what I sent:
When a customer attempts to process a credit card via Express and it fails they are redirected to paypal.com with no error stating what has happened. It should redirect back to our cart with an error.
We use CS-Cart on the front end.
Here is the log from that particular transaction. See the last line.
Requests (http/https request)
URL: https://api-3t.paypal.com:443/nvp
Request: 'PAYERID=JCGYSU358FKJN&TOKEN=EC-1C973733AT7039800&PAYMENTREQUEST_0_PAYMENTACTION=SALE&PAYMENTREQUEST_0_CURRENCYCODE=USD&PAYMENTREQUEST_0_AMT=698.30&METHOD=DoExpressCheckoutPayment&PAYMENTREQUEST_0_INVNUM=USOR1543&BUTTONSOURCE=ST_ShoppingCart_EC_US&PAYMENTREQUEST_0_CUSTOM=1543&PAYMENTREQUEST_0_NOTIFYURL=https%3A%2F%2Fwww.usoffroad.us%2Fstore%2Findex.php%3Fdispatch%3Dpayment_notification.paypal_ipn&USER=brad_api1.usoffroad.us&PWD=D5ZQVTD4QZUQJWXL&VERSION=106&SIGNATURE=AFcWxV21C7fd0v3bYYYRCpSSRl31AXa06v8wvOE0rr9qZrKTZrxdH1QJ&ADDROVERRIDE=1&PAYMENTREQUEST_0_SHIPTONAME=Zach+Bigam&PAYMENTREQUEST_0_SHIPTOSTREET=209+Menxil+NE&PAYMENTREQUEST_0_SHIPTOCITY=Albuquerque&PAYMENTREQUEST_0_SHIPTOSTATE=NM&PAYMENTREQUEST_0_SHIPTOCOUNTRYCODE=US&PAYMENTREQUEST_0_SHIPTOZIP=87107&L_PAYMENTREQUEST_0_NAME0=Toyota+FJ+Cruiser+Winch+Mount+Bumper&L_PAYMENTREQUEST_0_NUMBER0=FJ-07&L_PAYMENTREQUEST_0_DESC0=Powder+Coat%3A+Black&L_PAYMENTREQUEST_0_QTY0=1&L_PAYMENTREQUEST_0_AMT0=649.00&PAYMENTREQUEST_0_ITEMAMT=649&PAYMENTREQUEST_0_TAXAMT=0&PAYMENTREQUEST_0_SHIPPINGAMT=49.30'
Response: TOKEN=EC%2d1C973733AT7039800&SUCCESSPAGEREDIRECTREQUESTED=false&TIMESTAMP=2018%2d06%2d01T20%3a51%3a30Z&CORRELATIONID=1d2daeda490a4&ACK=Failure&VERSION=106&BUILD=46549960&L_ERRORCODE0=10486&L_SHORTMESSAGE0=This%20transaction%20couldn%27t%20be%20completed%2e&L_LONGMESSAGE0=This%20transaction%20couldn%27t%20be%20completed%2e%20Please%20redirect%20your%20customer%20to%20PayPal%2e&L_SEVERITYCODE0=Error
...and PP's response