Hi,
It's probably because the layout overrides are not compatible with the new version of the layouts in HikaShop due to the integration of the microdata in the product page layout.
Go in the folder templates/YOUR_TEMPLATE/html/com_hikashop/product/ via FTP and rename the files one by one until you identify the one causing the problem.
Once done, you can either:
- keep the file renamed if the problem is solved and that it doesn't change your product page layout.
- contact the developer of the template to notify him about the problem so that he can provide an updated version of that file.
- edit the files via the menu Display>Views yourself and take the customizations from the file in templates/YOUR_TEMPLATE/html/com_hikashop/product/ and apply them to the new version of the view file.