I imported released products using “Items” entity of data import /export framework.
The data is inserted in the table and the released products are displayed in the Released products list page but when i double click and open a released product all the fields are empty in the details page.
It means that you don’t have related data in one or more joined data sources. It’s typically caused by data missing from InventTableModule table (you need all three modules for each item).
Sorry, I can’t debug it for you since I don’t have access to your data. But the task is simple in principle - you’re running a query and want to find which condition prevents the data from appearing. You have many ways how to approach your debugging, e.g. analyzing the query in SSMS, copying the form and gradually removing data sources and code, rewriting the query and trying to disable individual parts, and so on.
It might be even caused by some customization or so - it’s impossible to just guess what’s wrong in your system.