We’ve taken a look at your template. The problem was the following: to include a chart in a report, you need to 1) create an empty band in the report structure for this chart, 2) create a named region in the template file with the same name as this empty band, 3) create the chart within this named region.
Here’s the report you can check:
Book availability in department.zip (16.1 KB)
Maybe this sample project will also be useful for you.
We’ll update the Reporting documentation to make this use case more clear.