flash player cannot access microphone

On an iMac 2013 / Yosemite I cannot get access to the microphone (need it for a language course) - not in Safari nor in Firefox. I de-installed Adobe Flash Player including preferences and cache files, re-installed it anew, that didn't solve the issue.

When I access the same iMac as a guest user, it's working fine. What could be the culprit?

One little thing: if I'm on the Mac as regular user, the flash player setting-box comes in English; when as guest user, it comes in German (Computer language is German).

Thanks!