I cannot install Flashplayer because it keeps telling me to "Close Firefox", but Firfox isn't open. I have tried opening it and then force quitting.
I'm on a MacBookPro, OSX
Also, how do I find out if anyone has answered my question? Will I get an email, or do I have to keep coming back here, which takes about a zillion pokes.
Maybe it is still running in the background? Check with the Activity Monitor.
Restart your machine, then immediately re-run the installer.
This finally worked for me, W10, Firefox browser, after tearing my hair out for a couple of hours!!