Hello,
It might be possible that due to the modification in HikaShop 4 regarding the billing/shipping addresses ; there is no shipping address give to the plugin. While the billing address could be set-up as shipping address in the object, that might be the case in your configuration.
I'm working on a modification for the sagepay plugin to check the shipping object and use the billing one.
Since the shipping details are mandatory in SagePay, even if there is no shipping details, we have to put the billing details instead.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.