Issue with bootstrap navbar dropdown

CodePen link:

Can anyone help me understand why my Navbar dropdown menu button - Career - is not working? Nothing is happening when I click it.

Because I am a new user if I try to paste my code the forum kicks my post back because I can’t post more than 2 links.

Thank you so much for your help!

You must add the following external libraries (in this exact order), to use the drop down functionality of Bootstrap 4.0

Thank you very much! Everything is working now!

For some reason I thought codepen automatically put those in as they say,“behind the scenes.”

Link for update: