"Spotify no longer supports this version of Firefox. "

[KnooL]

I solved the issue by removing 0.0.0.0 redirector.gvt1.com from my hosts file. This entry blocks Firefox from updating the Widevine Content Decryption Module provided by Google.

If this doesn't immediately fix the problem for you, untick 'Play DRM-controlled content' under 'General'. This will force the uninstall of the DRM decryption module. Tick it again and visit Spotify to download the DRM module once again.

[hahcho]

Thank you! I was starting to think spotify messed up seriously their web client.

[yafmiko]

Hi KnooL, the disable-and-reenable-drm worked for me, thanks!

(disable drm checkbox, close ffox, start ffox, enable drm checkkbox, open spotify web player, get notification about installation of audio codecs, works.)

[joergumbi]

Unvortunately doesn't work for me.