Sequence is loading as individual clips in another sequence

Before when I created a sequence and dragged that sequence into another sequence it would automatically nest all the contents and input it into the second sequence but now when i drag the sequence into the second sequence it imports them as indiviual layers and clips. How can I fix it so that it nests the sequence and any changes to the original file get applied to the nested sequence? 

In the example below, when I drag "MAIN VIDEO" sequence into "FINAL COMP" I want "MAIN VIDEO" to be a nested sequence that autochanges when the sequence gets altered, instead of how its appearing currently.