Problem with Musescore Online Playback and Audio Sources

EDIT: I notice this is the wrong place to ask this question, this thread can be deleted; sorry!

Hello,

I am trying to replace the default Musescore Online playback by adding an audio source (i. e. a Youtube video). Despite the bars being correctly synced with the video as shown below, the playback is however still the default one (at least as tested by me online and on my Android phone, both logged in and out). Is this the case for others too? Might the problem be that the youtube video I have linked to the score is a private one?

Thank you for your time!