Thank you so much pandeyism for your help.

I finally figured out the problem.

It turns out that property msie was no longer supported from jQuery 1.9 library and above.

So, after removing pretty much all my css links and nothing still worked, I checked developer tools by clicking f12 and discovered there was an error:

Unable to get property 'msie' of undefined or null reference

I added the below code and now the attach button is showing up.

Again, thanks for all your help.

<script type="text/javascript">
    jQuery.browser = {};
    (function () {
        jQuery.browser.msie = false;
        jQuery.browser.version = 0;
        if (navigator.userAgent.match(/MSIE ([0-9]+)\./)) {
            jQuery.browser.msie = true;
            jQuery.browser.version = RegExp.$1;
        }
    })();
</script>