Forge Custom Field and UserPicker

I’m trying to create a custom field using Forge. I have created it using “forge create” and changed Edit method as follows. If I comment out “UserPicker” it displays the popup dialog for edit when clicked. But with “UserPicker” edit popup does not works. Just a spinner is displayed on the custom field and it returns to as if not clicked. No errors in the console. Is there a limitation on which Form elements can be used in Forge custom fields?

    <CustomFieldEdit onSubmit={onSubmit}>
          <DatePicker name="date" label="Appointment Date" description="Appointment must be made 1 day in advance"/>
          <UserPicker name="user" label="User" isMulti placeholder="Users"/>
    </ CustomFieldEdit>

PS: I have just added DatePicker to check whether the popup works or not. It is not needed. The issue is, only DatePicker works, only UserPicker does not works.