Form Issue with Spawn Pages on Mac vs. Windows

Hi everyone,
I would like your guidance, please. I have built a form that includes a Spawn pages. When the user ticks the box, the code below should run and aggregate the pages. It works fine in Acrobat Reader on Windows, but on Mac, it doesn't work (when the box is ticked, nothing happens). Any idea why? and if there is any solution please
Thanks a lot
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var checkbox = this.getField("Reader");

if (numPages > 1) {
var confirmed = app.alert({
cMsg: "Are you sure you want to uncheck the box? This will delete your current form.",
cTitle: "Confirmation",
nIcon: 2,
nType: 2,
});

if (confirmed == 4) {
event.target.value = "";
this.deletePages(1, this.numPages - 1);} else {
event.target.value = "Yes";
}
} else {
if (event.target.value !== "Off") {
this.getTemplate("Page2").spawn(1, false, false);
this.getTemplate("Page3").spawn(2, false, false);
this.getTemplate("Page4").spawn(3, false, false);
this.getTemplate("Page5").spawn(4, false, false);
this.getTemplate("Page6").spawn(5, false, false);
}
}