I'm getting a "sync error" in OneDrive for Business

First, right-click the OneDrive for Business icon in your notifications bar (in the lower left), and select “View Sync Problems” – follow the instructions there, which will normally resolve the issue.
Alternately, you can try un-syncing and then re-syncing the library.
For persistent sync errors, they’re almost always remedied by clearing your Office Document Cache.
First, make 100% sure you’ve stopped sync on all folders. This is to prevent accidentally deleting files on your site when you delete your local copies.
Then, you have two options:
1) Automatic method – use the “Nuke OneDrive” button in the Verbatim Settings. This usually works, but if not, try method 2.
2) Manually clear it. To do that:
a) Close all Office Programs
b) Ctrl+Alt+Del, Task Manager, and kill any leftover Office processes, including GROOVE.EXE and MSOSYNC.EXE
c) Go to c:\Users\\AppData\Local\Microsoft\Office, and delete the entire contents of the following folders:
c:\Users\\AppData\Local\Microsoft\Office\Spw
c:\Users\\AppData\Local\Microsoft\Office\15.0
c:\Users\\AppData\Local\Microsoft\Office\16.0 (or 14.0), depending on your version of Office.
If you get file permission errors when deleting, then you missed killing a process.
Then, resync your folder.