Scope

Why was PII Data Cleared automatically for customers?
Is there a way to retrieve the data?

How to ensure Customer Personal Information is not deleted automatically?

Solution 

The reason why your customers do not have a name associated with them is that they had a subscription with them previously which was canceled & since these subscriptions were not reactivated before the 14-day period, their Personal Identifiable Information (PII) data was cleared.

There is a setting for this that would be enabled on your site that clears the data automatically. 

If you wish to disable this, you can do so by navigating to Settings ->> Configure Chargebee ->> Personal Data ->> Clear Data Automatically.

Now to retrieve their data, you would need to navigate to events under each customer, you can choose an event that was prior to the subscription cancellation that would have all the details of the end customer. 

On the customer information page, we will have the events tab, you should be able to get the events prior to subscription cancellation.

Related Article

Once PII is deleted for a customer, can a new subscription be created for them?

How is "Clear Personal Data" different from "Delete Customer"?

Unable to see the "Clear Personal Data" button for users