@Claudio0907 : I assume you've made sure the players on those pages aren't muted, nor do you have the tabs those sites are open in set to muted?
Then type about:preferences#permissionsData in the URL bar, then press ENTER. Check under "Speaker" to see if those sites are listed there, then go back and look under "Autoplay". The default there is "Block Audio" -- try changing that to "Allow Audio and Video".
Beyond that, an extension you use could be causing the issue. Try Menu -> Help and Report -> Troubleshoot Mode and if LinkedIn and WhatsAppWeb play audio fine in that mode, an extension you use is causing the muting in normal mode. See if you can disable one on those pages, and narrow-down which is causing it
