Firefox 52 dropped support for NPAPI plugins

[khanning]

Firefox version 52 has removed support for NPAPI plugins. This means that the Scratch Device Plugin will no longer work in Firefox. Firefox ESR will continue to support NPAPI plugins until early 2018.

Since serial device connections are not working properly with the Chrome version of the plugin (#55), Firefox ESR is currently the only option for people using the Arduino, iRobot, EV3, or any other serial device extensions.

[lmayorgav]

i still can´t install the extension even with firefox ESR

[jim-stoll]

FWIW, I the plugin is working under Safari (v11) on Mac (Sierra), and IE (v11) on Windows 10.

[cotestatnt]

Waiting for a definitive fix, i solved with a Firefox portable version 51.0 32bit where i copied the plugin dll in ..App\DefaultData\plugins.
Not elegant, but it works!

[towerofnix]

Note there will almost certainly never be a fix to this. The ST plans to deprecate ScratchX once Scratch 3.0 is released, as 3.0 has its own built-in extension system (which will eventually include extensions created by third-party developers). Scratch 3.0 comes with a tool called Scratch Link, which is designed to replace the Scratch Device Manager and is more reliable on recent systems (AFAIK there's no problem with it on Firefox, although I haven't tested it myself).

[JanusChoi]

Try a few work-around and I've given up this solution and turn to use s4a refer to s4a.cat.