If you're having trouble syncing some files in OneDrive for Business it may be because the files contain unsupported characters or name. Microsoft is updating OneDrive all the time as these do change from time to time too.
The following characters can not be part of a file or folder name....
" * : < > ? / \ |
The following file names are also not supported....AUX, PRN, NUL, CON, COM0, COM1, COM2, COM3, COM4, COM5, COM6, COM7, COM8, COM9, LPT0, LPT1, LPT2, LPT3, LPT4, LPT5, LPT6, LPT7, LPT8, LPT9
The final limitation to be aware of is the maximum path length can not exceed 400 characters, this includes the file name and all the folders it sits within, for example...
"Company\Health and Safety\Manuals\first aid at work.docx" - this full path contains 53 characters.
For the latest information on OneDrive restrictions view the Microsoft knowledge base article as it does change from time to time.