Location &1, product &2: Demand cannot be fulfilled

What causes this issue?

The demand for product &V2& at location &V1& cannot be fulfilled: There
is no initial stock, no production, no transportation lane, and no
external procurement. Moreover, it could be the case that a
transportation lane exists, but the source location cannot fulfill the
demand.

How to fix this error?

Check the modeling of your problem.

Error message extract from SAP system. Copyright SAP SE.