Verify that you do not have more than 20,000 individual files OR that the size of any single file(s) does not exceed 10GB as these are both OneDrive for Business limitations. Possible errors include: "This file is too big to upload" or "Reduce the size of this file to upload to…"
- If you think you have an unaccepted file type or any invalid characters that are not allowed in OneDrive (like a " #? " symbol or a ".tmp" type of file) then you need to rename the file without the symbol or convert/remove and that should fix the syncing problem with that individual file.
- Here is a full list of characters that are unsupported in the names of OneDrive files