Material & already exists

What causes this issue?

You wanted to create a new material master record, taking the material
number as a reserved material number from a different application (for
example, CAD).

System Response

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

How to fix this error?

The material master record does not need to be created because it
exists already.

Error message extract from SAP system. Copyright SAP SE.