The app be may be having issues since more than 1 problem is occurring. I’d Try to reset, then repair if that doesn’t work. (Save all your notes to another location, preferably external media before this, just in case)
Click start - settings - apps - onenote - advanced - reset. See if you can now save/and your files sync. If no luck, click start and type control panel. From there open programs and features. Then find office/onenote on the list and right click and repair.
See if that helps.
I’m also happy we were able to find them!
Let me know if I can do anything else, and If not, Have yourself a great rest of your week, and please leave a positive review if possible!
Thanks!
- C