Symptom:
Certain files and folders are not synching to OneDrive Personal using ECHO.
Cause:
OneDrive will not sync files that contain invalid file or folder names which contain invalid characters, reserved words, or sequence of characters.
Resolution:
Rename the files or folders to conform with Microsoft's requirements on valid file and folder names.
More Information:
For a list of invalid characters, reserved words or sequence of characters, please refer to the article: Invalid file names and file types in OneDrive, OneDrive for Business, and SharePoint