The tool was unable to create the Document Set

Symptoms

Sharegate displays the following error: 

The tool was unable to create the Document Set. Either you are unauthorized or there are required fields in your Document Set. Please note that this tool cannot create Document Sets with required fields.

Error code

Details

This error occurs because Sharegate is unable to create the Document Set in the destination library. It might be because you are not authorized to do so, or because you are copying to SharePoint 2010 and there are Required columns in your document set. Sharegate does not support creating Document Sets with required columns in SharePoint 2010. The reason for this is that SharePoint 2010 does not offer services for client applications such as Sharegate to create Document Sets with all the values filled-in. Sharegate needs to create an empty Document Set and then update it with the right values, which does not work if the Document Set has required columns.

It might also happen if you try to create a Document Set under another Document Set (SharePoint does not support nested Document Sets).

Solution

1. If you are copying to SharePoint 2010, go in SharePoint in your destination library settings. Then, click on the Document Set content type and, for every Required column except Name (which is always required), click on the column to edit its settings and set it to Optional. This will allow you to copy your Document Sets with Sharegate and, once the copy is over, you can go back in SharePoint to restore the settings as they were previously.
2. Make sure you are authorized to create Document Sets in the destination library. This can be easily tested by going in your browser and connecting to your destination SharePoint site with the same user account as you use in Sharegate. You can then navigate to the destination library and manually create a Document Set to see if it works.
3. Make sure you are not trying to create a Document Set under another Document Set. If this is the case, you can either change the top-level Document Set to be a folder instead of a Document Set, or copy your new Document Sets directly at the root of the library.