Hi Alexis,
We had analyzed your shared image. We suspect that an issue might be due to the absence of script manager in master page. If script manager is not present, then controls will not be rendered.
We suggest you to include the script manager in layout page as
@Html.EJ().ScriptManager()
If you are creating a sample using project template, then this will be automatically included in layout page.
We had prepared a sample in MVC for DropDownList control. Please refer the below given link:
We had also included this in our documentation. Kindly refer the below link
Regards,
Keerthana.