You notice the following error message in your migration logs :
Start() Error for email@example.com : Unable to connect to the target : Unable to login to ‘firstname.lastname@example.org’ Cannot contact site at the specified URL https://yourcompany-my.sharepoint.com/personal/user_company_com.
Cause 1 : During File Migration
This is because the OneDrive account for this user has not been provisioned.
To check if the OneDrive exists, as administrator of your Office 365 domain, go to this URL:
Replace -my.sharepoint.com with your company name
Replace user_company_com by the user’s email of the OneDrive that you want to check (don’t forget to replace ‘.’, ‘@’, … by ‘_’ in the URL).
If you get “Page not Found”, the OneDrive has not been provisioned.
To solve the problem, provision the OneDrive profile either by asking the user to log on to his OneDrive or by running the preprocessing task on this user.
Cause 2 : During Site migration
The site you are trying to connect does not exist in SharePoint Central administration.
To solve the issue, create the site collection on SharePoint Central administration and relaunch the migration once the site is created.
Cause 3 : During Site migration
The Target Site Collection field in the sitelist is not correctly filled. The Target Site Collection must be filled in with the site collection’s relative URL.
Put the right site collection relative URL in the field Target Site Collection
For example, if the site collection URL is: https://company.sharepoint.com/sites/test, the Target site Collection should be sites/test
Note: please especially check if there is no any spaces characters in your URL string.