Hi Rajesh,
Thanks for contacting Syncfusion support.
We suspect that you would have not referred contextMenu dependency CSS file in your sample. So that, the contextMenu is not rendered in your sample. Please import that CSS file in your sample as shown below. However, we have missed to specify it in our documentation. We will include it and let you know once refreshed online.
Code example
Please find the sample as below.
Regards,
Ramya T