JAWS Screen Reader is not detecting the dynamic value of textbox

Question

I am developing a combo box which predicts the cities from the city list. When the user types the minimum of 3 letters and if the city list box has at least one search result, the result should be auto populated to the textbox without using the down arrow key.

For ex: if the user types SYD and if the predicted result has SYDNEY,Australia , the value of the textbox will be dynamically updated to SYDNEY,Australia.

NVDA is reading the updated text SYDNEY,Australia. JAWS is reading only those 3 letters(SYD) but not the updated text.

I have set the following attributes to the textbox "aria-autocomplete":"both","aria-live":"assertive"(have tried all the 3 values of aria-live). Still it couldn't help.

var myTimer;

this.element
            .addClass( "ui-autocomplete-input" )
            .attr( "autocomplete", "off" )
            // TODO verify these actually work as intended
            .attr({
                role: "textbox",
                "aria-autocomplete": "both",
                "aria-haspopup": "true",
                "aria-live":"assertive"
            })

The following code is to select values from the city list:

clearTimeout(myTimer);
    thisInstance = this;
myTimer=setTimeout(function () {
      if(thisInstance.menu.element.find('ul li.ui-menu-item a.ui-corner-all').length == 1) {
            var event = jQuery.Event("keydown");
            event.which = 0;
            event.keyCode = 40;
            
            var item = thisInstance.menu.element.find('ul li.ui-menu-item');
            thisInstance.menu.active = item.eq(0).children('a')
                    .attr("id", "ui-active-menuitem")
                .end();
                thisInstance.menu._trigger("focus", event, { item: item });
        }}
        , 600, this);

Could anyone please answer?