When using the Select Same Paint option from the Select menu, not all objects with the same active Paint Style are selected.
In a file that contains several white objects with 0% for all the separations, not all 0% objects are selected when you:
select an object
use the Select Same Paint option.
This is not considered to be a bug, because ArtPro displays only 2 decimals in the separation percentage values. Which means that if you define a value of e.g. 0.001% in the original application, ArtPro's user interface displays it as 0%. So even though objects appear to have the same Paint Style in the user interface, their values can be internally different.
How to select all 0% objects in this case? In the Paint Style window, use the All Zero button for problematic objects. You can:
Select all problematic objects and use the All Zero button for all the selected objects at once.
Select an individual problematic object and use the All Zero button for that particular object only.