How to create Purchasing Categories?

Summary:

Advise needed to create Purchasing Category

Content (required):

We need to create new Purchasing Categories and do nominal mapping.

Created Purchasing Category in Functional Area Catalog, and used the name in Nominal mapping set.

But few of the categories are not reflecting the nominal, and few does.

Please advise if I am missing any step or is there any nomenclature to be followed and any character restriction for creating Category name and Category Code.

Thanks in Advance

Version (include the version you are using, if applicable):

21D

Code Snippet (add any code snippets that support your topic, if applicable):