1. Switch to the Database View.
  2. In General Ledger > select Configuration > Tables > Media Type.
  3. Click 'New Table Entry' to add a new Attachment type value.
  4. Save and Close.
  5. Add the attachment in FENXT.

Note: if you're trying to add an attachment to a deposit from the Treasury menu, you'll want to make sure you go to General Ledger > Configuration > Tables > Treasury Media Type to add new type values.