Why does my sandbox subscription not match my production account subscription? Why is my sandbox missing features?
The subscription on your sandbox matches the subscription you had on your production account when the sandbox was created. If you change your subscription after creating your sandbox, the new subscription won't automatically sync over to your sandbox. To sync your subscription, reset and wipe out your old sandbox to create a new sandbox that has the latest subscription. See how to reset your sandbox in this article: Replacing your sandbox.
A number of features and settings do not copy over to your sandbox account by default. To see a list of which features are copied over, see this article: About Zendesk sandbox environments.
However, Zendesk offers a premium sandbox that allows you to copy over more data from your production account. You can read more about the premium sandboxes in this article: About the premium sandbox.
If you need to configure additional syncing from production to your sandbox, use the REST API to copy data in your production account and create it in your sandbox.