How to utilize FEFO Lot Assignment feature? Netsuite is still asking for manual entry

We have lot numbered items. Everytime we fulfill an order, user has to click on Inventory Detail for each item and select the lot/bin from there based on the list he has sorted by expiration date. I thought FEFO Lot Assignment feature was a remedy for this situation. I installed the bundle, set up preferences for the location, but fulfillment still asks us to click on Inventory Detail and pick a lot. It doesn't matter if I click on Fulfill, or the newly added "Assign & Fulfill" buttons on the Sales Order, fulfillment screen is still expecting user input