It would appear that Java is blocked in Firefox 64-bit.
From: Mozilla Blog: Use the Java plugin to view interactive content on websites
Mozilla plans to drop support for all NPAPI plugins except for Flash in March 2017, when Firefox version 52 is released.
Note: The 64-bit version of Firefox does not recognize or support this plugin.
Also from Mozilla Forums: No Java plugin
Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:43.0) Gecko/20100101 Firefox/43.0
You have the 64-bit version of Firefox, where only Silverlight and Flash Plugins are 'whitelisted'. If you need Java you need to install the 32-bit version of Firefox. You can have both the 64-bit and 32-bit versions installed, but you'll need to do a "custom" installation (on the first screen of the installer routine) and select or create a uniquely named folder - like maybe Firefox 32, otherwise the 32-bit installer may overwrite your 64-bit Firefox installation.
This is probably due to the ongoing drive to eradicate insecure and NPAPI-based plugins.
From a security standpoint, this is A Good Thing (tm), but from your standpoint you need to use a 32-bit version of the browser.