What causes this issue?

You defined an interchangeability relationship 'Substitution for
Remanufactured Products' for product &V4&. The predecessor product &V4&
at location &V1& is defined as planning relevant in the location product
master data. The successor product &V2& at location &V1& is defined as
not planning relevant in the location product master data. DRP
determines a substitution demand for the successor product &V2&. Because
the successor product &V2& location &V1&is not planning relevant, this
demand is not considered in the DRP planning.

System Response

DRP will not place the substitution demand on a non-planning relevant
location. The system will issue an error message and place the
substitution demand for product &V2& at the parent location &V3&.

How to fix this error?

Please review your interchangebility definition and the
stocking/destocking parameters for the product &V4& and product &V2& at
location &V1&. The planning relevance needs to be synchronized. With the
current definition deployment can not cover the demand at this location.
In SAP Standard the replenishment indicator ST (stocked) has DRP
planning relevance per default. You may want to set the successor
product &V2& at location &V1& to replenishment indicator ST (stocked)
and run DRP to redetermine the result.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.