No delivery proposal for FU &1: delivery is blocked for planning

What causes this issue?

Technical explanation:
Field BLK_PLN of the freight unit root data contains the information
indicating whether this freight unit is blocked for planning. If the
switch 'Exclude FUs/FOs Blocked for Planning' has been activated in the
delivery profile, only an empty value is allowed in field BLK_PLN.

System Response

This freight unit is excluded from the creation of delivery proposals.

How to fix this error?

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

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.