Hi there!
I think this error is because maybe Eli Book is not updated on the sample project, Try to update Eli Book and Choice manager to the last updated versions and see if it will work.
It's kinda complicated. I'm on the processo to remake a lot of stuff, probably that sample project will be remade from scratch too. If the above did not solve, I will try to see if I can upload a new version. But it may take a while. Can you tell me what do you want to do with choice manager? Maybe I can help with that