I just installed mint 18 64 bit and then the plugin for create. restarted firefox and it doesn't find the plugin even though it is a green icon on the tray. Create also doesn't work in Mint 19, Windows XP (32 bit) and it barely works in Windows 7. It took a week to start working. Sometimes the mint 19 would recognize the icon, but then refuse to upload even though the board and port were selected correctly and the Create webpage recognized that and Uno had been plugged in on that port.
What is needed is more control releasing a piece of software. It has wasted a lot of my time and probably a lifetime's worth of time around the world.