Your internet speed probably is the reason for the malfunctioning of your audio and video. Go to the test page to check your internet speed. If the test indicates that your internet speed is too low you might be able to switch to another internet connection. Refreshing your browser with F5 can possibly solve the problem.
You can refresh your video stream with F5. This solves the problem in most cases.
The webinar is probably playing simultaneously in two or more browsers. Please close all expandable browsers and continue watching in just one browser.
If you’re watching from a corporate network or with a VPN connection, you might experience some problems. Please close this connection, if possible, and open a permissible browser to watch the webinar.
Your screen is probably zoomed in. Click Ctrl+0 to recover this.
In some browsers, you need to switch Flash on manually, after installing the player.
The links below help you though the right steps, per browser.
Google Chrome: https://helpx.adobe.com/nl/flash-player/kb/enabling-flash-player-chrome.html
Internet Explorer: https://helpx.adobe.com/nl/flash-player/kb/install-flash-player-windows.html
Internet Explorer op Windows 10: https://helpx.adobe.com/nl/flash-player/kb/flash-player-issues-windows-10-ie.html