I have Windows 10 with Firefox 57 and Flash Player work correctly. To install or update flash player, you must going to Adobe's Flash Player download page and download the Flash installer.

https://get.adobe.com/flashplayer/

More information : https://support.mozilla.org/en-US/kb/keep-flash-up-to-date-and-troubleshoot-problems#w_installing-or-updating-flash

For ShockWave (not Flash) : https://get.adobe.com/shockwave/

I have the Flash Player. Pls note I am inquiring about Adobe Shockwave Player!

Firefox Releases since 52.0 only allows the Flash Player from Adobe to run in Firefox whether on Windows, Mac OSX, or Linux.

https://support.mozilla.org/en-US/kb/npapi-plugins

The Firefox 52 ESR mentioned in bottom of article does still allow other NPAPI Plugins to run in Firefox.

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I have Firefox Quantum and downloaded Adobe Flash Player. on my Toshiba Satellite laptop. Shockwave Flash 28.0 r0 is activated in Plugins. I have done everything suggested & still I can't play videos....grrrrrr! WTF is going on? Anything else I can do? Don't get to technical as I am not all that technically literate,..thx!

Hi Fishnet, if you can't play videos on mainstream video sites, it's likely to be an issue with the built-in HTML5 player and not Flash.

When you ARE on a site that uses the Flash plugin for video, you would see the plugin notification icon at the left end of the address bar (dark gray "Lego" block indicates Flash is activated for the site, light gray block indicates you need to activate it on the site).

Could you start a new question with your system details? As always, scroll down past suggestions to continue with your question.

https://support.mozilla.org/questions/new/desktop/fix-problems

As part of your description, could you indicate which boxes on YouTube's test page are "blue" vs. "red": https://www.youtube.com/html5