Greetings from Syncfusion support.
While checking the provided screenshot, you have rendered the EJ2 DatePicker component but installed the EJ1 Core NuGet packages and imports the tag helper o for EJ1 DatePicker component.
So, If you want to render the Syncfusion EJ2 DatePicker component, you need to install the “Syncfusion.EJ2.AspNet.Core“ NuGet package and imports the tag helper “@addTagHelper *, Syncfusion.EJ2“ to render Syncfusion EJ2 ASP Net Core components.
Please find the UG link from below.
Else, if you want to render the Syncfusion EJ 1 DatePicker component means, please make use of the below code as showcased in below UG documentation.
<ej-date-picker id="startDate" value="DateTime.Now" html-attributes="htmlAttr"></ej-date-picker>
Still issue persists, please revert us with issue reproducing sample and whether you want to use EJ1 or EJ2 component that will help us to check and proceed further at our end.