You are migrating to OneDrive and during Pre Processing task, your drive is stuck in Pending status.
When you create a user, the OneDrive profile is created on the fly the first time that a user tries to access their OneDrive.
However, it’s possible to programmatically pre-provision the OneDrives.
See Microsoft article: https://technet.microsoft.com/en-us/library/dn800987.aspx
This is what is performed during the Pre Processing: a request is sent to Office 365 asking to provision the OneDrive. However, this is an asynchronous task and it only queues the request on Microsoft side: it could take some time to be executed by Microsoft.
If the drive is in Pending status, it indicates that there is a bottleneck on the Microsoft side. The requests are still queued and not executed. The Cloudiway platform will check every 15 minutes if drive is provisioned and if yes, the status Not Started appears.
The only thing to do is to wait until Office 365 executes the request.
You can also ask the user to login to their OneDrive in order to trigger the creation of their profile immediately.