My AT content type can't be added TTW

I must confess that my custom Archetypes packages are all created with zopeskel, by the time it worked like advertised. I do not find the step-by-step docs for mr.bob to create a simplest Archetypes package, so here is how I just work with a vanilla Plone 4.3.12 instance:

First, install ZopeSkel 2.21.2 (not 3.x), update in your buildout.cfg or develop.cfg

parts =

# installs paster and Zopeskel
recipe = zc.recipe.egg
eggs =

Then pin ZopeSkel to version 2.21.2 (say, in version.cfg or buildout.cfg). Run buildout and you should see zopeskel and paster in bin folder.

$ cd src
$ ../bin/zopeskel archetype MyCompany.MyProduct

archetype: A Plone project that uses Archetypes content types

This creates a Plone project that uses Archetypes content types.
It has local commands that will allow you to add content types
and to add fields to your new content types.

If at any point, you need additional help for a question, you can enter
'?' and press RETURN.

Expert Mode? (What question mode would you like? (easy/expert/all)?) ['easy']:

Develop the package with buildout. Then create the Archetypes type with paster. See

$ cd MyCompany.MyProduct
$ ../../bin/paster addcontent contenttype
Enter contenttype_name (Content type name ) ['Example Type']: MyType
Enter contenttype_description (Content type description ) ['Description of the Example Type']:
Enter folderish (True/False: Content type is Folderish ) [False]:
Enter global_allow (True/False: Globally addable ) [True]:
Enter allow_discussion (True/False: Allow discussion ) [False]:

Finally, you will see MyType from the Add new ... menu.

I believe there's a good reason to deprecate paster and zopeskel. However, the existing docs I could find is to utilize ZopeSkel. And I also believe you can directly adapt Dexterity types to meet your needs. Consider migrating your Archetypes items to Dexterity. Good luck.