Designer will no longer launch with the latest update of FireFox. Searching this forum and on line the only information I can find is that Firefox will no longer support .jnlp files and consequently no longer offer the plug-in for the latest FF versions.
Is there a work around for this?
Native Client Launchers. Download from gateway home page. Run and point at gateway. Pick designer or project.
Like Phil said, the NCL is your best bet. But you should still be able to download the jnlp file for the designer and then double click that to open – once you’ve downloaded the file, Firefox isn’t involved at all.