Pay Pal Standard - loading Pay Pal login page not payment page

This was working fine in July 2019, but after a period offline to resolve other issues my integration is not working. Nothing has been changed at my end. The IPN link all looks fine. I have GF 2.3.6 and GF Pay Pal Standard 3.1.

Any reason why the submission to Pay Pal is returning the Pay Pal login page and not the payment page with the pay by card option

I recommend opening a support ticket for this issue, thank you: