Hi,
I have that problem, I say on title. I don't know why when the scene changes and want to start a dialogue, it doesn't work. Screenshot of the errors I got:
In the Dialogue Editor, make sure the correct actors are assigned to the conversation's Actor and Conversant dropdowns. Their names will be shown in a watermark in the lower right of the Dialogue Editor.
If you're using Dialogue Actor components to change the subtitle panels that actors use, make sure the subtitle panels exist in the new scene. Please read this to get an understanding of what could be the issue: How To: Manage Player Controls and Scene Changes