Frontend Invoice Printing Do not show custom field

Hi,

I checked the code of the view file which displays the invoice and the order details view (it's the same view file for both) and I don't see any reason a custom product field would show for the details page and not the invoice.
Check if you have the file templates/html/com_hikashop/order/show.php via FTP.
If you have it, rename it temporarily and check the situation on an order again.
If it displays fine, it means that it comes from some modifications done on your end in that view file override.
So I would recommend to redo the override in the backend and check the situation each time you do a modification so that you can find which modification is causing the problem.