Partner &1 is blocked; only deletion is possible

What causes this issue?

Partner &V1& is blocked; see long text

System Response

You want to change data for partner &V1&. The data related to this
partner may include personal data and is blocked. You can only delete
this data.

How to fix this error?

If you are sure that you want to create or change data for this partner,
use transaction BUP_REQ_UNBLK to request unblocking.

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.