Tracking protection is enabled by default in Firefox and this blocks the mailchimp signup form JS code.
The Firefox console shows the following message upon loading the page:
The resource at “http://downloads.mailchimp.com/js/signup-forms/popup/unique-methods/embed.js” was blocked because content blocking is enabled.
Here you can see mailchimp.com is in their block list
I'm not sure but a quick Google turned up some mentions of embedding the form instead to avoid this.
Another option perhaps is a notification of some kind like this one
Tracking protection is enabled by default in Firefox and this blocks the mailchimp signup form JS code.
The Firefox console shows the following message upon loading the page:
Here you can see mailchimp.com is in their block list
I'm not sure but a quick Google turned up some mentions of embedding the form instead to avoid this.
Another option perhaps is a notification of some kind like this one