I'm having a unique challenge and thought I would put it out there. I have successfully synced selected folders from Teams and Channels to my Mac. I can see that when new files are added, they do make their way down to my local folder.
However, when I save a new file to a synced folder, it doesn't upload up to Teams or SharePoint.
I have noticed a que of these files in OneDrive which is perpetually "updating files" but the files aren't getting uploaded.
I've done the usual, check for updates and restarted.