If you’re creating an ASG using an AWS Launch Configuration, you cannot use a name for the Launch Configuration.

The solution? Simply omit name from your launch configuration.

https://github.com/hashicorp/terraform/issues/3665

Launch Configurations cannot be updated after creation with the Amazon Web Service API.

https://www.terraform.io/docs/providers/aws/r/launch_configuration.html#using-with-autoscaling-groups