There is a known issue with games like Farmville 2in Firefox 40

https://developer.mozilla.org/en-US/Firefox/Releases/40/Site_Compatibility#Plug-ins

You can turn off the new feature that seems to be causing this issue and see whether that resolves it:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.

(2) In the search box above the list, type or paste ipc and pause while the list is filtered

(3) Double-click the dom.ipc.plugins.asyncInit preference to switch its value from true to false

I don't know whether that starts taking effect immediately, or whether you need to exit Firefox and start it up again.

Then return to the page with the game and reload the page (you can click the circular arrow in the address bar) to see whether it will work now.

Any luck?

jscher2000 said

You can turn off the new feature that seems to be causing this issue and see whether that resolves it: (1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful. (2) In the search box above the list, type or paste ipc and pause while the list is filtered (3) Double-click the dom.ipc.plugins.asyncInit preference to switch its value from true to false I don't know whether that starts taking effect immediately, or whether you need to exit Firefox and start it up again. Then return to the page with the game and reload the page (you can click the circular arrow in the address bar) to see whether it will work now. Any luck?

You will need to close Firefox for the new config setting to take affect. If you want to see simple screen prints of the required actions see my post at > screen prints for simple fix