Pop Up Not Working

I’m trying to get a simple Email Subscriber pop-up added to my homepage. I’m using a Auberge Child Theme (so possible you can’t help – though all I’ve changed is CSS code form the original theme) and the plug in Hustle, though I have tried other pop-up plug ins with the same outcome.

It simply…doesn’t do anything. I have no idea what could be the problem, so I’m anticipating clashing code, but don’t have the first clue what to edit to get my pop-up to work. The Hustle set-up instructions indicate that I’ve done everything and it should be working but I’m cross-posting to their help board too.

Any ideas? My site is https://www.brm-studio.co.uk