The resolution for this issue depends on whether you work with Insane Mode on Microsoft 365 or with SharePoint on-premises.
Index
Symptoms
When attempting to copy an item, ShareGate Migrate displays one of the following error messages.
The permissions for '<USER>' were not copied because '<USER>' does not exist at the destination.
The group '<GROUP>' was not found at the destination. The selection group filter was reset to all users.
The group's owner '<USER>' cannot be found at the destination. The current user will be used instead.
The user '<USER>' could not be created/found at the destination. This is probably because the user was either deactivated or deleted in the Active Directory.
The user or group '<USER_OR_GROUP>' is required for this workflow and cannot be found at the source (or destination).
The owner of the term set could not be found at the destination. The current user has been assigned.
No owner was set on the Term Set. The current user has been assigned.
The following users and groups were not found: John Doe
Property 'Editor': The user 'john' could not be found at the destination. The current user has been assigned.
The workflow refers to the user 'john', but this user could not be found at the destination. It might prevent the workflow from executing correctly.
The alert 'UserAlert' refers to a user account with id 1 which could not be found at the source. It may have been removed from the user information list.
The alert 'UserAlert' refers to a user account with id 1 which could not be found at the destination. It may have been removed from the user information list.
The default group '<GROUP>' will be ignored because it could not be found at the destination.
The list is configured to mask users.
Error codes
DA-064-080
DA-067-080
DA-078-110
DA-083-115
DA-078-249
DA-083-249
ST-037-080
ST-042-080
ST-056-080
ST-109-080
ST-122-080
ST-126-080
ST-130-080
ST-137-080
ST-225-080
ST-363-080
AN-002-080
AN-063-080
Any error code ending with: -110 or -80 or -115 or -249
Details
The error occurs because the specified user or group is not considered valid by SharePoint.
To be considered valid, your user or group has to be in the User information list of the destination site collection or active in your destination's Active Directory.
The most common cause for this are users who have since left the organization.
When ShareGate Migrate creates or updates your users and groups, SharePoint does not accept your source users or groups that are not currently valid in the destination.
You can learn how to address the error based on your scenario below.
Permissions
You cannot assign permissions to an invalid user at the destination. To keep these permissions you must assign them to a valid user by mapping the invalid user or group to a valid user or group.
Microsoft 365 destination
You can only retain an invalid user or group metadata value when you migrate to a Microsoft 365 destination in Insane mode.
This is because Insane mode uses the Microsoft 365 migration API which accepts invalid user values.
Note: Insane mode is not supported in certain cases. When you migrate a library with content that is not supported, that library is migrated in Normal mode and when that happens, SharePoint will no longer accept invalid user or group values for the whole library. In these cases you can handle your users as you would in an on premises SharePoint destination as described in the next section.
On-premises SharePoint destination
It is not possible to retain an invalid user or group metadata value in the user or group column of an on-premises version of SharePoint.
If the user information is not important, the simplest method to handle this issue is to map your invalid users to a default user.
If you are required to preserve your user or group information, you can map the user information to a new text field in SharePoint.
Note: This process requires that you use Copy content only for the migration and you will need to create a new column in your SharePoint library manually.
To preserve your user information, follow these steps:
Open your destination library in SharePoint.
Go to your list or library settings.
In the Columns section click Create column.
Give the new column a name like Original assignee.
Select Single line of text as your column type.
Click OK.
Open ShareGate Migrate.
Select Copy in the menu.
Select Copy content only.
Click Connect.
Select your source site, and select your source list or library.
Click Next.
Click Connect.
Select your destination site, and select your destination list or library.
Click Next.
Click Mappings.
Select the Properties tab in the mappings screen.
Find the source property that contains the invalid user metadata in the first column (for example Created by).
Drag and drop that source property next to the new column you created in your list or library.
Click Save.
Select your items.
Click Start copy.
ShareGate Migrate will now take the users and groups from the source and write them as simple text in the new text field.
Note: ShareGate Migrate will try to add the invalid user in both the original user column and the new text column. This means that you will still see the missing user warning in your migration report.