The preferred language is Swedish, which is a ridiculously small language and not on the priority list of Apple, but I run all programmes I can in English.
When changing the preferred language to English (UK), the sentiment analysis started working.
I believe that sentiment analysis is not yet available in Swedish.
Yes, you are probably right. It would be great if Tinderbox would allow to select a language instead of having to change the preferred language on the entire computer, which I am not sure is possible at all. However, I can live with setting my preferred language to English anyway…