No task list maintained for prod. version & (selection w/o prod. version)

What causes this issue?

During routing selection, the system searches for production version
&V1&. However, there is no routing in the material master for this
production version.
Therefore, routing selection occurs according to the following
selection criteria:

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

Material number
Plant
Lot size
Status
Key date
Usage
Planner group
The system takes into account the selection criteria of the selection
ID as well as the selection criteria entered.

Error message extract from SAP system. Copyright SAP SE.