There may be instances that the "Delete" option is disabled in Cloud One console. This is because you may be using a Cloud Connector for your Cloud Accounts (AWS, Azure, GCP, and etc.) to link it to your Cloud One - Endpoint and Workload Security account. The only way to delete the unmanaged machine in your account is to terminate the instances itself in your Cloud Accounts(AWS, Azure, GCP, and etc.). Once done, the machine will also be removed in your account.