Can't install Flash - Installation failed This week my El Capitan system reported that the Flash player was out of date.  So I did the usual thing and went to Adobe, downloaded the latest (21 A) installer and kicked it off. After entering my password, the installer went through the usual "downloading .." part and commenced on the installation part, at which point it failed, showing me this:



What I did was the same as I had done many times before, but this time it failed - and I tried multiple times and also downloaded the installer multiple times.  

Any ideas?
I had this problem on &amp; off for years, it's something to do with my firewall, which I've never been prepared to fiddle with just so I can get an online installer to function properly. 

The simplest workaround is to go get the full downloadable .dmg version instead of the online installer.

For the past few years, it's been located at http://www.adobe.com/uk/products/flashplayer/distribution3.html
or you can Google "adobe flash player offline installer download" which always finds it.

I did eventually find a solution to my Flash problems...
... I uninstalled Flash from every machine in the building ;-)