I have tried to view other's Snapchat stories, but when I press on their username on the My Friends list there is no drop down menu. What should I do?
You should check the timeline as well for the stories. There are a few causes to this issue:
You are not their friend anymore, even if they're still on your list.
The stories expired, therefore you can't view them anymore.
Your friends didn't post any new stories, that's why the lack of the necessary buttons.