When migrating content from Box or DropBox to SharePoint Online (SPO) or OneDrive for Business Online, Box and DropBox groups are not migrated properly even though they are mapped in the CSV User Mapping file.
The CSV User Mapping file must be in a specific format, which includes the title row. If the title row is missing, the Box groups will not be migrated. The Box and DropBox groups must be mapped to the Claim ID of the AD Group in Office 365.
Use a properly formatted CSV User Mapping file when migrating content to Office 365. Below is an example:
|Box User||SharePoint User Found|