Forum Discussion
Browser and app not the same
The issue you are experiencing where you only saw one person and an excel document doesn't sound like something I have heard before so I urge you to contact support with that issue if it happens again. you can open a case at answers.microsoft.com and they can assist you with troubleshooting.
That said, there are different ways to view your class - either by using the Microsoft Teams client you download on your computer, via the web app - which sounds like what you were doing, and the mobile app. I would highly recommend you download the Teams client if you are going to be joining a team or Teams calls, regularly. Here are instructions for the various clients: https://docs.microsoft.com/en-us/microsoftteams/get-clients
There is some limited functionality using the web client with a Mac such a limited video views, etc - that is documented in the link above. If you can, download the full client and for attending meetings and quick chat functionality, the mobile client is wonderful. Personally, I prefer the desktop client for collaboration and interactive meetings. I hope that helps!