A family of Microsoft products that enable users to capture, organize, and reuse notes electronically.
Dear Yat-Ho,
sorry for I can't reproduce your issue, that I have no education account of Office 365.
in my pass experience, while the page has nothing loaded, it seems you couldn't access the Notebook page normally, or the page was broken.
after turned on external sharing in SharePoint online, if the issue still occur,suggest you raise a support ticket from the Office 365 admin center, where the related team will collect the logs and find out the cause of the problem. Reference: Get support - Microsoft 365 admin | Microsoft Learn
If you need any further assistance or any misunderstanding from our end, please feel free to post back to us.
Thanks for your patience and understanding. Have a good day!!
Best Regards,
Sophia