Customer &1 is blocked; see long text

What causes this issue?

You want to display or change data related to a customer. The data for
the customer may include personal data and is blocked.

System Response

The system does not display any data related to the customer to protect
personal data, and you cannot change data for this customer.

How to fix this error?

If you are sure that you want to display or change data related to the
customer, use transaction BUP_REQ_UNBLK to request unblocking. Ensure
that this is compliant with your organization's policies.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.