I've been using Opera for a while, on an Ubuntu 64 distribution.

Suddenly today, the google hangouts plugin stopped working; specifically, when I try to start a hangout, the plugin installation page shows, and even if I (re)install it, the same happens again.

On opera://plugins, I see only the flash player, and the pdf viewer.

I'm using opera-beta (35.0.2066.35), but the problem happens also on opera-stable (I'm using opera-beta (35.0.2066.37).

I have auto-updates set on my O/S, so it's possible that some update suddenly broke things between yesterday and today, but there is nothing which is obviously broken (Firefox recognizes and uses the plugin without problem, currently); also, the plugin (v5.41.0.0) hasn't been updated since 26/March/2016.

How can I diagnose the problem?
Thanks.