If you are using Zoom on a Chromebook, you must install the Progressive Web App (PWA) in order for all features to work.

Here is the link to install:

https://play.google.com/store/apps/details?id=us.zoom.pwa.twa  

1. To get started, open Google Play on your Chromebook and then search for Zoom for Chrome PWA. 
2. Click and install it on your Chromebook.
3. Next sign in with your Credentials. You’ll be presented with a super simple interface where you can set up a new meeting, join one or schedule a Zoom meeting. You get all the features you will find on Native Mobile or Desktop zoom apps. 

More information: https://support.zoom.us/hc/en-us/articles/4403638230925-Using-Zoom-for-Chrome-PWA