Shipping type & does not match shipping type & for route &

What causes this issue?

The shipping type of the item does not match the shipping type assigned
to the route.

System Response

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

How to fix this error?

Enter a shipping type that is the same as the one in the route. .
The shipping types must be the same so that the deliveries can be
selected for the shipment.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.