Materials are still allocated to material group &

What causes this issue?

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

System Response

How to fix this error?

You cannot delete the material group if materials are still assigned to
it. You can check which materials are currently assigned to the
material group by choosing the menu options Goto -> Display MG
material.

Error message extract from SAP system. Copyright SAP SE.