How strange, it works for me (using Erel's example). I even tested because I was bored
1st option: --> add that line to the manifest (it isn't there in the original example)
<item name="android:textSize">44sp</item> '<--------------------HERE
2nd option.--> Without adding that line in the manifest, and using CSBuilder (just checked it and if the line is present, overrides size changes of CSBuilder)
The only explanation I can think of is that there is more than one "myPopupMenuStyle" and depending on device density (just a guess) is using one or the other. In my case the used one was the third. But if you put the same line in all three should give the desired effect (or if you remove it from all three, then it should be possible to change size with CSBuilder)
<style name="myPopupMenuStyle" parent="@style/Widget.AppCompat.Light.PopupMenu">
<item name="android:popupBackground">#FF0AECD3</item>
<item name="android:textSize">44sp</item> '<-------------------- PERHAPS ALSO HERE
</style>
<style name="myPopupMenuTextAppearanceSmall" parent="@style/TextAppearance.AppCompat.Light.Widget.PopupMenu.Small">
<item name="android:textColor">#FF0000</item>
<item name="android:textSize">44sp</item> '<-------------------- AND HERE
</style>
<style name="myPopupMenuTextAppearanceLarge" parent="@style/TextAppearance.AppCompat.Light.Widget.PopupMenu.Large">
<item name="android:textColor">#FF0000</item>
<item name="android:textSize">44sp</item> '<-------------------- AND HERE (this is the one that worked in my device)
</style>