Thanks for using Syncfusion product.
We are not able to reproduce the mentioned issue of”ContextMenuOpening event not get fired when click on appointment”. We have created a sample with custom radial menu. Please find the sample in the below link.
Sample Link: CustomRadialMenu
Could you please modify the above sample to reproduce the issue and revert us back? So that we can analyze on the issue further and provide you a possible solution.
Please let us know if you have any concern