Hello,
By the way, are you using OneNote for Microsoft 365 on your Windows PC, or the OneNote app from Microsoft Store?
What you are seeing lines up with a recent OneNote update on Windows. Microsoft updates OneNote on Windows more often than on Android, so visual changes like checkboxes turning into circles show up on PC first. Each platform handles formatting differently, even when you use the same account. This change likely came with the January 22, 2026 Office or OneNote update, not with a Windows system update. Your notes are not damaged. This is a display change only. Once the Android app receives the same update, the icons should match.