check your mozilla firefox plugin folder for the following files:
C:\Program Files\Mozilla Firefox\plugins
npdsplay.dll
npdrmv2.dll
npwmsdrm.dll
alternatively you can type '
aboutlugins' in the firefox address bar.
if the files above ^^ are not in the folder, download them from below and place them in the plugin folder.
npdsplay.dll
npdrmv2.dll
npwmsdrm.dll
restart firefox..
test everything at a website like putfile.com
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if that doesn't work, i suggest you follow
this guide