You most-likely have the option “Respect Do Not Track settings in browsers” enabled in the plugin, found under Wizard > General > Security & Consent.
Meaning that if the plugin detects a Do Not Track signal from the browser (which browsers such as Firefox have enabled by default), the plugin will automatically assume all your cookie preferences to be “denied”, and doesn’t display a banner as a result.
Disabling that option in Complianz, or disabling the “Send a Do Not Track” option in your browser, will resolve this behavior and cause the banner to appear.
This feature was previously a part of the Premium plugin, but is now included in Free as well.
In any case, I see the following message when visiting your site in Firefox with Do Not Track enabled. So I would still expect that my previous answer is applicable in your case: