Suddenly I started to get error when I try to open my dropdown menu :
bootstrap.min.js:6 Uncaught Error: Bootstrap dropdown require Popper.js (https://poppe
In the introduction of Bootstrap it states which imports you need to add. https://getbootstrap.com/docs/4.0/getting-started/introduction/#quick-start
You have to add some scripts in order to get bootstrap fully working. It's important that you include them in this exact order. Popper.js is one of them: