I appreciate your willingness to help me with my problem.
I have been able to create a PayPal sandbox account and a test buyer account and successful process test purchases. Each time when the test buyer returns to my website the download link is available and working.
However, when I go back and change the Quick Sell configuration back to my regular selling PayPal email address and to live transactions, I still get the endless loop. I called PayPal and that email address is a valid business account in good standing.
So I'm really stumped as to why my Quick Sell configuration works with the Sand Box selling and buying accounts but won't work with my regular selling PayPal account and a regular PayPal buyer account. I even tried buy without an account just using a credit card.
The transactions are recorded at PayPal but the confirmation never makes it back to my web site to enable the download. I'm really confused.
Please / Thanks for any suggestions on where to look.
Spike