Open quantity no longer exists

What causes this issue?

Item &V1& (&V2& &V3&) is to be assigned an association.

System Response

An association can only be assigned to an item if it has a quantity
that has not yet been associated.
As item &V1& is already associated in full, processing is terminated.

How to fix this error?

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

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.