How to use PLSQL to set value of Popup LOV with Multiple Values

I am running an application on Oracle APEX 21.2 and ran across a problem with a Popup LOV page item with the Multiple Values setting turned on. The Popup LOV works as expected up until the point when I try to load data into it from the database or from a static value using PLSQL within a dynamic action of Page Load. When setting the value of the Popup LOV using PLSQL, it will not display the values correctly. It's as if the control is not taking into consideration that it is a multiple value Popup LOV when displaying the data.