The first thing you should try is to make sure that you have the latest Java.

Java security settings are set too high.Firefox is created by a global not-for-profit dedicated to putting individuals in control online. Q: How safe is it to use Firefox on Mac A: Its relatively safe but its commonly out of date so its no where near as safe as using Apple Safari web browser. You are using outdated Java (below Oracle's security baseline). Download Mozilla Firefox for Mac, a free web browser.Synergy products, please install a specific version of Firefox ESR that is specifically. If a web page with Java Uploader or Downloader displays correctly, but does not upload or download chosen files, this may mean two things: Mac Users: Install Firefox Version Compatible with Silverlight. If you click the Allow now button, you will encounter this problem again when visiting other web pages that use Java. When you click Allow and Remember Firefox adds the current webpage to an internal whitelist, whereby the Java applet will run automatically in the future without further intervention.

Firefox for mac