Since 30/09/2011, it seems Mac has changed the way to check the certifs.
This affects webcams on : Mac/IOS with Chrome and Safari.
Problem is the way browsers do check the HTTPS certificates generated with LetsEcrypt.
The solution to solve these issues is to edit config.js on mediasoup server and change
/etc/letsencrypt/live/mysite.com/cert.pem -> /etc/letsencrypt/live/mysite.com/fullchain.pem