MS Teams - Class Notebook sync issues

Hi,

I'm having an issue with Class Notebooks on Microsoft Teams.

Upon adding users to the Team, they automatically get their own area within the Class Notebook. For some reason now, when adding another user it does not appear to have created them an area.

I have tried opening in OneNote so I can sync them but I keep getting this message:

But I am of course, connected to the internet. I'm not too sure what to do, it's baffling me.

Thanks