I'll spare the rage and get to the point.

I'm unable to open my files in OneNote. I simply don't understand how this software works.

I think what happened was that my OneDrive became too large and my OneNote documents could not sync with it. I ignored this since I don't care about OneDrive. I continued to use OneNote with it unable to sync to OneDrive.

Then one day, upon starting OneNote, it couldn't find my notebook files (I forget the exact error message). I realized if I went to tripleline->MoreNotebooks->My Notebook it restored my files. But the files seem to be the last version that were able to save to my OneDrive before it was unable to sync due to lack of space. So several months old.

I suspect my actual up-to-date OneNote data is still saved offline in my Documents folder. But... I have no idea how to open this. Whenever I try I get the message "We can't create a page here. Try reopening your default notebook." I don't know how to "reopen my default notebook" since this software lacks any kind of command to "open" files. This error message has 1 google result that doesn't even address the problem. Wonderful.

I'm wondering if I may have to make space on my OneDrive so the my offline files can sync. But now that I've opened the older OneDrive files, I'm afraid they will overwrite my offline files, if they haven't already. Maybe I need to delete the OneNote files in OneDrive, free up space in OneDrive, then upload my offline files. But most likely I need to throw my computer in the garbage and jump in front of a train because I don't want to live in a world where something can be this awful.