@burnout426 Yes, I tried everything in Opera, but it seems that nothing works.
Thanks but leave it like this, how in a couple of months there will be a big update of Windows 10, I will format everything and do a complete installation from scratch. I will download everything again from its original pages. What I need to know is how to access the hidden options of the Opera browser.

Thanks again for your time and sorry for the inconvenience.

I've taken a look on opera://media-internals, on "Audio" tab found this:

{
  "AudioServiceAudioStreams": "Disabled",
  "AudioServiceLaunchOnStartup": "Disabled",
  "AudioServiceOutOfProcess": "Disabled",
  "AudioServiceOutOfProcessKillAtHang": "Disabled",
  "AudioServiceSandbox": "Disabled",
  "WebRtcApmInAudioService": "Disabled"
}

[]

I don't know what this is for and how to activate those options.

Thanks burnout426, but I set up sound from "automatic" to "allow" option long time ago and the issue still there.

I'm working on Windows 10 Pro. This sound issue just happening on Opera browser, on the other ones works fine. By the way, I'd been format once and installed the Opera browser again and audio issue from twitter an Whatsapp still there.

Sounds and video on youtube works fine using Opera Browser, why sound doesn't work on twitter and whatsapp?

I'll take a look what you said, about opera://media-internals.

All my system has the last updates.

Note: Sorry about my gramar, I'm from spain and I dont't speak English very well even writting.

All audio message from Opera Whatsapp no sounds at all, and many of video from twitter can't hear anything. It's just happen on Opera Browser only. It's happening since long time ago.