Mobile menu randomly stopped opening

Today when on my website on my phone I tried opening the menu by clicking the hamburger button and the menu wouldn't appear. 

The click of the hamburger button is recognized as the header changes colour and the hamburger button turns into the close button. 

Not sure what would have caused this, and my limited debugging knowledge couldn't find out why. Any help is greatly appreciated.

Live site is: https://porterrentals.ca