ctkDICOM example can not display images thumbnails

[renyuhuiharrison]

I have built the latest CTK library and examples successfully with VS2019(MSVC 16.4) . I launch the example ctkDICOM with a DICOM directory. The app can list all the series of DICOM data. But the thumbnails on the bottom can not display when I expand the node in the tree widget(As the following picture). And it seems to fail to expand all slices tree node of one series. The code of example is not modified.

This is the debug output information in the console:

I have tried Debug and Release mode, but all failed to display the thumbnails. So can anyone give me some tips? Thanks in advance.

[lassoan]

You may need to enable thumbnail generation in the indexer.