Salesforce Marketing Cloud Account Engagement Tracking Cookie

I'm working with a Salesforce consultant to add a Salesforce Marketing Cloud Account Engagement/Pardot tracking cookie on our site so when our Salesforce prospects visit our site, their engagement is tracked. 

We've done this before, but although the tracking cookie is injected, it will not work. 

We've troubleshooted in the header, then in the footer, we've activated the cookie banner so visitors must opt in, but nothing seems to be activating the cookie and getting it to work. 

Can anyone provide insight and other work arounds? Surely we're not the only squarespace customer looking to do this. 

It's challenging to find any resource on this.