I'm trying to submit an MDF Request for a Partner, but they're not showing up in the MDF Request Owner dropdown. What's going on?

There are a number of reasons why a Partner User might not be showing up in the MDF Request Owner dropdown:

• The User doesn't exist.
• The User is not Active, e.g. the User is a
  • Pending User. You can only assign MDF Requests to Pending Users by changing this setting.
  • Contact. Contacts cannot log in or be assigned MDF Requests.
  • Disabled User.
• Permissions: The User isn't assigned to a Group with MDF Module access.