Asset class & does not exist for main asset number

What causes this issue?

You want to create an asset sub-number. The existing main asset number
has been created in class &V1&.
Asset class &V1& does not exist.

System Response

Processing termination.

How to fix this error?

The system has determined inconsistency between the asset master record
and the asset class. There must be an asset class for the existing
assets.
Contact your Systems Specialist.

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.