Version & does not exist

What causes this issue?

You want to pass on data for product group materials to demand
management, and you want this data to represent specific proportions
of product group planning. A special version has been declared for this
purpose, but it does not exist for this product group.

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?

Error message extract from SAP system. Copyright SAP SE.