The Store cart summary behavior is only supposed to create one record. The summary should contain information about the person who placed the order and where it is to be shipped.
The store cart details server behavior will store a record in the order details table for each line item in the cart.
Sometimes the session form the Store Cart summary behavior will not populate in the bindings panel, if it is missing, you can add it manually. copy the session name form the save as option in the Store Cart Summary, then go to the bindings panel. Click the Plus button and select Session Variable, then paste the name to create the binding.
If the Summary is being stored in the database, but the details are not, the most likely problem is that a redirect has been set in the Store Cart summary behavior. Do not set a redirect in the Store cart summary behavior so that the code can progreess to the store cart details.
If you are still having problems, please send a copy of the page so I can examine the code to see what is wrong.