OneDrive AutoSave isn't working, and it's creating new files instead of saving over my original file.

That's the problem. They changed it so that AutoSave creates the new file. That's how it's "supposed" to work now, and they think it's helpful. I've yet to find one person who likes this new change.

I'd suggest don't even use AutoSave anymore. Just manually save the file each time you've make changes. If you have your Desktop synced to your OneDrive, the file in OneDrive will sync too.

Do you know where they documented this is how it is supposed to work now? Given that when I open the file in one way, AutoSave is off, and when I open it a different way, AutoSave works, I'd like to know which one is the bug based on the current documentation.

This is truly absurd. Who wants multiple copies or versions of a document? It takes up twice as much disk space and if you're not careful, you will edit the wrong version. I am taking an online class and wrote a paper. I closed my document and went to the school website to upload it. I inadvertently uploaded an earlier version that had some mistakes and was incomplete. My teacher graded it and when I realized what happened after the submission deadline, he allowed me to submit the "good" version, but only gave me half of the points back that he took off. I have been using another cloud service called IDrive and think I'm going to ditch OneDrive. Why would MS fix something that wasn't broken??

That's the problem. They changed it so that AutoSave creates the new file. That's how it's "supposed" to work now, and they think it's helpful. I've yet to find one person who likes this new change.

I'd suggest don't even use AutoSave anymore. Just manually save the file each time you've make changes. If you have your Desktop synced to your OneDrive, the file in OneDrive will sync too.

There is another solution. You go to your OneDrive folder by internet, not in your computer, you chose your file there and you chose either to open excel by internet or, as I prefer, use Excel on your desktop. Like this you have only one version by internet that is get modified.

I cannot have multiple versions since I share the same file with other people. It is real absurd to create multiple files, I totally agree.

So now I have 2 files. One is in OneDrive/Documents (the changed version) and the unchanged version is in OneDrive\Other\Recipes

The new file (the changed version) is what you want, isn't it? Your work is saved and thankfully you don't need to start over each time. Both versions are in OneDrive.

OneDrive\Documents is the syncing system folder when Documents syncing is toggled on at Manage Backup. OneDrive\Other\Recipes is not in the Documents folder.

I share my original file with another people. I don't need to create multiple versions of the same file each dayt I open a file. I need one file that sync with all that I can use everyday and not to create duplicates.

The registry fix provided by @Ferreira Cédric didn't help.

Manually installing updates in Office only helped a little (https://support.microsoft.com/en-us/office/install-office-updates-2ab296f3-7f03-43a2-8e50-46de917611c5)

I found that when I launch a Word (.docx) file from File Explorer or a terminal (start "My/file.docx"), AutoSave is turned on. When I launch the Word document from Everything (https://www.voidtools.com/), AutoSave isn't turned on. So, that leads me to believe that there is a problem with AutoSave when files are launched using a certain API. Anyone have any ideas about this?