The EAN & cannot be used as the supplier-specific EAN

What causes this issue?

You have specified the International Article Number (EAN) &V1& as the
supplier-specific EAN. However, this EAN cannot be used for one of the
following reasons:
The supplier-specific EAN does not exist.
Before a supplier-specific EAN can be created, it must exist as an EAN
for a unit of measure in the relevant material master record or be
created in the same transaction.
The EAN for the relevant unit of measure has been deleted.
As a result, it may no longer exist as the supplier-specific EAN.
The EAN for the relevant unit of measure has been changed.

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?

Depending on the cause:
Create the EAN as a normal EAN for a unit of measure.
If the EAN for the relevant unit of measure has been deleted, you must
also delete it for all suppliers.
If the EAN for the relevant unit of measure has been changed, and you
still want to use the EAN for this unit of measure as the
supplier-specific EAN, you must change it to the new EAN for all
suppliers concerned.

Error message extract from SAP system. Copyright SAP SE.