PayPal Not Return to correct page on completion

I have s2 Member Pro and have generated the paypal form. The paypal form collect the money correctly but will not redirect the user to a welcome page.

My PayPal has the auto return URL correctly.

The PayPal also has the ENCRYPTED payments as OFF.

Instead the user is send to the payment form again with a simple success statement on top.

I suspect the problem is S2 member rather than PayPal but I can’t find where.

Any help appreciated.

Bob