Checkout as guest while having an account.

-- HikaShop version -- : 6.1.0
-- Joomla version -- : 5.4.0
-- PHP version -- : 8.3.x
-- Browser(s) name and version -- : safari latest

My client is having issues where users who registered before but now want to order as guest are unable to do so. Why is this restricted and how do i make sure this is possible?