The browser is probably blocking the request is your admin panel is under SSL/HTTPS. The upgrade URL is a normal HTTP:// url
You could change line 44 of oc-admin/themes/modern/tools/upgrade.php
from
$.getJSON("http://osclass.org/latest_version_v1.php?callback=?", function(data) {
To
$.getJSON("https://osclass.org/latest_version_v1.php?callback=?", function(data) {