Pie chart using JSON data

Hi

I want to create a pie chart and my datasource is JSON (this data is returned by REST-API)

The chart will be to show Online and Offline host information

So far i have created a sub-dataset with 3 fields ie, hostID, hostName, hostState

Created a group on hostState.

Pie-chart's key is hostState, value is counter created on group (hostState_count).

Reset and increment both are set to group hostState.

But when i preview the chart, i only see one group in whole pie (ie. only Online hosts show up with single slice) 

Am i missing something ? Please help