One possibility is that you have one or more file paths exceeding 255 characters, not too hard to do since Onedrive is by default already located at a fairly deep level (c:\Users\YourUsername\Onedrive).
Here is a great free utility which can find these files so that you can fix them: http://www.replsoft.com/cutlongnames.html
Another easy action that has fixed a lot of OneDrive issues for me is:
Right-click on the OneDrive master folder and click properties, then Security tab, then the Advanced button at the bottom.
Click the check box at bottom "Replace all child object permission entries with inheritable permission entries from this object." (Some guides say to ensure first that Owner is your username, but it always has been for me already.)
Click ok and wait, may take 30min+ depending on how many files you have. Sometimes it looks frozen but just leave it alone and it does end up finishing.
OneDrive should start working normally pretty quickly after that.