You cannot select Change Retail Mat. by Material Master for Standard Mat.

What causes this issue?

Retail articles cannot be modified with Master Data Maintenance using
the current configuration.

System Response

You cannot create retail articles using Material Master Maintenance when
the <ZK>Material Creation</> parameter is set to <ZK>Standard Material
</>.

How to fix this error?

Set the parameter to <ZK>Retail Material</> in Customizing by choosing
<ZK>Materials Management -> General Settings for Materials Management ->
Enhanced Material Search -> Configure and Activate Enhanced Material
Search with Creation</>.

Procedure for System Administrators

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.