Hi,
The upgrade doesn't change the way your settings are setup.
However, what you're describing means that you where using an old version of HikaShop, and you updated to the 4.4.0.
The 4.4.0 is a major update, where we removed legacy settings. You must have been using the legacy add to cart system before which automatically redirected to the checkout be default, while the new add to cart system (added since HikaShop 3.0.0) doesn't.
But you can activate that back in the settings of the HikaShop cart notification plugin via the joomla plugins manager