The best way to open a notebook that’s saved on SharePoint is to use the free OneDrive Pro app that’s available in the App Store.
Once the OneDrive Pro app is installed, follow these steps to open the notebook:
From the OneDrive Pro app, tap the notebook you want to open.
Tap , and OneNote will automatically open the notebook.
Your organization may require you to setup a VPN connection on your iPhone to access SharePoint notebooks when you’re not connected to the network. If you’re having trouble accessing a SharePoint site, this might be the cause. If you’re not sure if you need to use a VPN connection, please check with your network administrator.