Requirements class & is not defined

What causes this issue?

The system has classified the business transaction that you are
processing as Requirements class &V1&. This has either not been
specified or is not designed for a business transaction in SD.

How to fix this error?

The requirements class is taken directly from
<DS:GLOS.requirements_type>requirements type</>. Please check your
entries there.

Error message extract from SAP system. Copyright SAP SE.