Hi Massimo,
Greetings from Syncfusion support.
On inspecting the sample provided, we have found that
you have not added the cdn link for importing the css. Please refer the below
code for adding the css.
Sample: https://codesandbox.io/s/musing-buck-wnmgn4?file=/public/index.html:571-665
Please get back to us for further details.
Regards,
Joseph I.