Dear Victoria,
first: thank you so much for answering. On a Saturday… that can count as a service!
The issue seems to be solved, but I hav eno idea how. It might have to do with the use of some type of YouTube links that gives this error message, coïncidally at the same time where I changed the ‘fase’-‘true’.

As for now it seems to work, so sorry for bothering you!
A mute/unmute button that the visitor can use to either mute/unmute the video sound might be a handy option in the future?

best wishes,
Wim