When displaying the Donor Wall shortcode, it is currently not possible to filter by the Form ID unless using the Shortcode Builder.
The Shortcode Builder creates: [donor_wall form_id="23"] for example
The form_id attribute cannot be used when manually building out the Donor Wall Shortcode.
As a workaround, we recommend using form= instead of form_id=. Example below:
[give_donor_wall form=987] or [give_donor_wall form="987"]