turn off styling for a single block

The issue is that the embedded code has defined a class of .header but doesn't have any CSS for it. Squarespace does have declarations for that class and so the embedded code is picking up styles from Squarespace. This is basically what you described.

Without going into details the cleanest way I can see to solve the issue is add the following to a code block.

<iframe srcdoc="

  <div id=&quot;geotix-widget-container&quot;>
  
    </div>
    
  <script src=&quot;https://d1wcopahj6rhb7.cloudfront.net/events/prd/geotix-embed-latest.js&quot;>
  
    </script>
    
  <script type=&quot;text/javascript&quot;>
  
    // CSS Override Documentation
    // https://s3.amazonaws.com/geotix-widgets/events/css-customizations.md

    GeotixWidget.fetchTickets (

      {
      
        token : 'e4a16f02280cdf1ee211ade00d4eaeee',
        
        container : 'geotix-widget-container',
        
        portalId : 102
        
        }
        
      );
      
    </script>
    
    "
    
    style="border : unset; height : 100vh; width : 100%;"
    
    >
    
 </iframe>

Using an iframe tag isolates Squarespace from the geotix code. Using an iframe can have it's own challenges but in this case I think the downside is less problematic than other approaches that might be used.

Let us know how it goes.