Values for object & incomplete (characteristic & has no value)

What causes this issue?

When you call matrix processing, the calling transaction must transfer
several tables to the matrix. These tables contain the axes of the
values to be displayed, describe the possible nodes, and so on. These
tables must be consistent. In the current situation, the description of
at least one node was transferred to the matrix in table VAR_ART.
However, the values assigned to this in table VAR_MSEL are not
complete.

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

System Response

How to fix this error?

This error can only be corrected by correcting the interface program of
the calling transaction.

Error message extract from SAP system. Copyright SAP SE.