Using sagepay_server gateway in test mode can get to payment page fine but on submit I get sagepay errors:
HTTP Status Code: 500 HTTP Status Message: The request was unsuccessful due to an unexpected condition encountered by the server. Error Code : 5006 Error Description : Unable to redirect to Vendor's web site. The Vendor failed to provide a RedirectionURL.
Return URL is in place in the checkout tag, using return="shop/order/ORDER_HASH" which usually works fine.
Settings for clients sagepay account are correct.