Custom API - User Role Not Available

I'm trying to set up a Custom API with Influitive with LaunchPoint. I've followed the instructions from both of these articles:

Create an API Only User Role - Marketo Docs - Product Docs

Create an API Only User - Marketo Docs - Product Docs

and am attempting to continue using Create a Custom Service for Use with ReST API - Marketo Docs - Product Docs - however, when I go to define my Custom service, nothing populates in the API User Only field/dropdown, nor can I type anything into that box. Since it's a required field, I'm stuck on this step. I've tried to rename the user role, add additional privileges to the role. Help!