I presume you're running Photoshop CC.
The Flame Generator filter is in Photoshop CC 2014.
That's a whole new version of Photoshop after CC - not just an update to CC.
Thank you for your answer, John.
Yes, I am running Photoshop CC but am paying the photographer's subscription and assumed I therefore qualify for all ongoing developments. Does this mean that I now need to install CC 2014?
CC 2014 is a separate install via the Cloud desktop app.
It's included in your membership but it does not install automatically. You must choose to install it then the Cloud app will keep it updated for you.
Once installed, ensure that your Photoshop icon in your taskbar is for CC 2014. Many people install CC 2014 but leave the old CC icon on the desktop and confuse themselves by launching CC when they've got both CC and CC 2014 installed.
Thank you very much for your time