Most times when pages aren't loading in the OneNote app, the issue can be fixed by simply signing out of the app, then signing back in.
Step 1: In the top right of the application the user will see thier name displayed. Click the name.
Step 2: A window will pop up in the center of OneNote. Click "Sign out."
Step 3: Select "Remove" on the account removal confirmation.
Step 4: The user will automatically be prompted to sign back into OneNote. Select "Work or school account" and click "Continue."
Step 5: Follow prompts to sign into Microsoft account as usual.