kfitzsimI just went through this problem and noticed that many people had it and there were all sorts of super techie answers. This ended up being my super simple answer.
Problem: I had logged in to my website using /wp-admin and there was no longer andy drop down options for Plugins and no button for Themes.
Solution: I clicked on Network admin in the top right. All the buttons I was looking for were there.
I don't know the program all that well but thought it might help someone else to post this!
