A user defines Event Rules and sets a value in Walk_In_Fields_vod. The new field of Attendee cannot be added on the Register form of Walk-in Attendees in CRM iPad.
The user only defines the new field on EM_Attendee_vod. The field must be on both the EM_Attendee_vod and the Event_Attendee_vod objects.
Define the same new field on Event_Attendee_vod also.
The user must have Field-Level Security (FLS) edit permission to the fields to display on the registration form.
CRM Help Documentation: Walk-in Attendees