Trainable Weka Segmentation doesn't work


I’ m trying to count number of cells from histological image.
Therefore, I want to use “Trainable Weka Segmentation”.

However, it doesn’t work.
The error is “Plugin or class not found”.
I want to know the improvement method.

I have tried ①install fiji ②install Trainable Weka Segmentation ③renew java.
Could you tell me about the way of working?

I’m in a pretty pickle.