You can take a look at our demos which can be found at C:\Program Files (x86)\Progress\Telerik Reporting[Version]\Examples\CSharp
and compare your project with them.
From the given information, I cannot define what is in the root of the problem. Are there any errors in the browser console?
You may use Fiddler
to look at the request to the REST Service and see whether any of them fails and why.
You may also open a support ticket and give us more details about the issue. For example, you may attach the project so that we can take a look at it and come up with particular suggestions.
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Feedback Portal
and vote to affect the priority of the items