When System Administrator profile is deployed through metadata, got the following error.
Unknown user permission: ManageSandboxes
Then I logged into my target organisation and checked
Setup -> Profiles -> System Administrator -> System Permissions. The
ManageSandboxes permission was not availble under the
Users section at the bottom of the page.
But this setting is available in all the other sandboxes and in production instance as well.
All sandboxes and production org have
Summer 20 release.