Inconsistent definition of view cluster & (not activated)

What causes this issue?

The View cluster definition contains an error.

System Response

The View cluster was not activated.

How to fix this error?

Remove the error and re-activate the View cluster.

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

The View cluster activation log contains a list of errors.

Error message extract from SAP system. Copyright SAP SE.