Paypal [Return to Merchant] button not returning

[drobert]

Hi All,

I'm running Joomla 3.7.5 and Virtuemart 3.2.4.
Using PayPal Standard payment method.

When a payment is made at PayPal the [Return to Merchant] button does not return to my website, it returns to PayPals home page. I have read "How to configure PayPal and other questions" and related posts and can't find a solution
* The Apache log shows no incoming requests from PayPal when the [Return to Merchant] button is clicked
* I've turned on the virtuemart log in the payment method and only see:
2017-09-07 06:43:30 DEBUG plgVmConfirmedOrder:
2017-09-07 06:43:30 MESSAGE plgVmConfirmedOrder:
* I've turned on the virtuemart debug and the [return], [notify_url], and [cancel_return] parameters look correct. They just don't seem to be used by PayPal.
* The orders stay in the Pending state. So no IPN is getting through - also nothing in Apache logs to indicate an IPN.
I don't know what else could be wrong.  Please help.

Thanks,
-dr