When attempting to copy an item, Sharegate displays one of the following error messages:
Unable to determine web context for root item with scope '<URL>'
This error occurs while copying a site object to a destination site when Sharegate is unable to determine into which site at the destination the object should be copied. When copying site objects, Sharegate attempts to recreate the structure as accurately as possible to match the structure from the source site. For example, if a list is using a Content Type that was created in the root site, it will attempt to create the Content Type in the root site as well on the destination site.
However, in some rare cases, Sharegate can fail to determine where it should be copied. This is often due to a configuration issue with the object itself, such as moving a site to become a sibling of one of its previous parents. The site object can then require a parent Content Type that is no longer available in its site hierarchy. This behavior is not supported by Sharegate and as such, the copy will not succeed.
You will need to contact Sharegate support at email@example.com in order to further investigate the cause of the issue and determine the appropriate course of action to resolve it.