'Where can I find the error messages for my PayPal transactions?'
'What are the descriptions for the error codes on Paypal?'
'How do I access the list of transactions and the relevant error logs?'
You can find the error codes in the 'transaction activity log' on the PayPal site. You can access the transaction activity log by following the steps given Here
The above link also has details on each error code and its description.