I am using Firefox. I have also followed Adobe's suggested procedures in checking that Shockwave is 'always enacted', etc
At a loss, really
Since you're using Firefox you'll need to install the NPAPI plugin. The PPAPI plugin is not compatible with Firefox. PPAPI plugin is for chromium-based browsers such as Opera. The NPAPI plugin is for Firefox and Safari.
I have that version already installed and I reinstalled it since but still to no avail. It has been since I updated to El Capitan