Fixed Starting Dates Shortcode not working

I tried to add Fixed Starting Dates to a Page or Post using the shortcode but it is not working.

Example:
I tried to add the Fixed Starting Dates of this trip: https://roger.gerstner.cc/trip/reise-test/

using this shortcode: [WTE_Fixed_Starting_Dates id=’23’]

To this page:
https://roger.gerstner.cc/test-seite/

But is shows nothing.

I tried that on different pages and posts.

Please help!