Hi Massimiliano,
Greetings from Syncfusion support.
Based on the shared information, we suspect that you might have missed to include the Material.css theme file in you end, which is required for rendering the control UI properly. Kindly include the following CSS file in your application.
<link rel='nofollow' href="https://cdn.syncfusion.com/ej2/material.css" rel="stylesheet" /> |
Let us know if you need any further assistance on this.
Regards,
Prince