Enter valid field name

What causes this issue?

The order or network type has no number range assigned to it.

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

System Response

You cannot maintain the order/network without the number range
assignment.

How to fix this error?

Maintain a number range in customizing for the order/network type.

Error message extract from SAP system. Copyright SAP SE.