Note that sometimes the latches won't quite close all the way on their own.
The process requires a bit of force, but if you’re having trouble, make sure that you’re not attempting to put the module in backward, or that one of the ends isn't out of alignment with the slot. Note that sometimes the latches won't quite close all the way on their own. After you're sure your sticks are fully inserted in their slots, you can nudge any latches the rest of the way closed.