Sandbox auto return doesn't return to seller site

[trebleman71]

 I have a live business account, I created my developer site, I created a seller and buyer account in sandbox. Logged into sandbox as seller, set the seller account to auto return to a thank you page on my live website,  created a Buy Now button to download a mp3 file. Put the button code in the button test page on the my live website. When I click the button on the button test page I can go thru all the steps to make the test purchase and at end of purchase the file is downloaded to my computer but paypal sandbox does not send me to the thank you page, it just displays that it is processing and never changes.

Here's the sandbox seller account button code:

<form action="https://www.sandbox.paypal.com/cgi-bin/webscr" method="post" target="_top">
<input type="hidden" name="cmd" value="_s-xclick">
<input type="hidden" name="hosted_button_id" value="MPFTYWJXAK22A">
<input type="image" src="https://www.sandbox.paypal.com/en_US/i/btn/btn_buynow_LG.gif" border="0" name="submit" alt="PayPal - The safer, easier way to pay online!">
<img alt="" border="0" src="https://www.sandbox.paypal.com/en_US/i/scr/pixel.gif" width="1" height="1">
</form>

How do I get the auto return to function correctly?

[MTS_Vimalnath]

Hi, I tested your button code and after the transaction is complete , I did return to the below URL: http://www.kevinwinchmusic.com/download/XXXXX.zip?amt=1.07&cc=USD&item_name=Brand%20New%20Day&st=Com... It looks like your Payment Data Transfer (PDT) is on , so it returned to the above URL. To make sure that auto return always works, please make sure you enable it from https://www.paypal.com/us/smarthelp/article/how-do-i-use-paypal's-auto-return-feature-to-redirect-cu... Note : If you've enabled Auto Return and have also enabled PayPal Account Optional for new non-paypal account users, they won't be automatically redirected back to your website, but will have the option to return.