A family of Microsoft products that enable users to capture, organize, and reuse notes electronically.
Good day Luis Vila,
From what you described, I understand that recent changes made on your iPhone and Mac are no longer syncing consistently across your devices.
Before troubleshooting, please copy any important unsynced pages or sections to a safe location. Then sign out of OneNote on the affected devices, restart OneNote and your Mac, and sign back in using the same Microsoft account.
Next, manually sync the affected notebook on both your Mac and iPhone by following the instructions in this article: Sync a notebook in OneNote
If the issue continues, open the notebook list and check for a yellow warning triangle beside the affected notebook. Hover over it and please share the exact error code or message displayed if available.
Please let me know how it goes, and thank you for your patience!