No leading unit of measure maintained in association group &1

What causes this issue?

The leading unit of measure is to be determined using association group
&V1&.

System Response

A leading unit of measure is not entered in Customizing for association
group &V1&. As a result, the leading unit of measure cannot be
determined.
Processing is terminated.

How to fix this error?

In Customizing, maintain a leading unit of measure for association
group &V1&.

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.