You cannot maintain production versions here

What causes this issue?

You wanted to maintain production versions. However, this is not
possible in the following cases:
When scheduling the creation or changing of a material
If you have not specified a plant
If you have not selected a view for the user department <LS>MRP</> or
<LS>Work Scheduling</>

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?

Check and extend your data as required.

Error message extract from SAP system. Copyright SAP SE.