We recently introduced the web version of our desktop app - the functionality should be the same on the web and in the desktop app.
In order to use the web app, you need a browser that supports Web-GL. To check whether your browser supports Web-GL, please use this link. After you click the link, you should see a cube - if you a see green spinning cube, then your browser supports Web-GL.
If your browser supports Web-GL, but Avocode on the web still doesn't work for you, it must have been disabled somehow.
The most common reason of disabled Web-GL is disabled hardware acceleration in your browser. To enable it, please follow this guide (for Chrome, Firefox, Safari).