Plug-In Failure: Safari/El Capitan Facebook game

I keep on getting a "plug-in failure" message on my desktop computer when trying to run a Facebook game (Coral Isle) in Safari. I have run disk utility/first aid, re-installed my OS (El Capitan), uninstalled Flash Player and re-installed. I believe this is a conflict with some other file on this computer, because I can run the game on my laptop, same OS, same Flash Player. Are there any known conflicts with Flash Player and other plug-ins or applications? The problem arose yesterday - prior to that I had no issues.