Displaying statistics

Hi,

For a few days now I'm trying to figure out why I cannot display desired statistics properly. If someone has any idea how to solve this it would be great.

Anyway, I have platform where users send questions to local government offices and they respond. Questions are sorted by administrator through taxonomy "in procedure", "solved", "answered" etc.

I want to show through PIE CHARTS number of questions under taxonomy "in procedure" and number of "solved/answered" questions. Percentage between them. Average time for answer (thats php computed field). Number of questions by taxonomies.

I managed to display in views number of questions (nodes) under taxonomy "in procedure", number of "solved/answered" questions and number of questions by taxonomies but when I try to display it through charts my result is missing, that is, chart is not displayed.

For eq. the simplest chart I'm trying to achieve is showing number of nodes by content types. I have two content types and results I get in regular view are correct. [attached image: views-regular-results] but when I try to switch that to pie charts I don't see results anymore. In image views-pie-chart you can see settings.

What I do:

Format: Views Simple Chart;
Settings: Chart Axis Mapping (Type,Nid)
Chart type: Pie chart

Fields:
Content: Type | Aggregation (Group results together)
Content: Nid | Aggregation (Count)

Also, when I switch to Bar chart in settings it show results (number) for only one content type...

I am missing something, but what?