Chat options not available - Teams App for Mac

drkings I'm not sure this will work for you or anyone here, but I solved it this way…

When I was using a Microsoft-supplied email address, registered via my company's IT department (for example, mailto:email address removed for privacy reasons the chat option wasn't showing. 

Invites to Team meetings are, however, sent to my regular, non-ms email address. For example mailto:email address removed for privacy reasons 

When I click an invite, I log in to Teams as my regular, non-MS company user (email address removed for privacy reasons). This seems to have put me in guest mode or something similar. In this mode, no chat window is shown or seemingly available.

I asked my IT department to use our company's custom domain for our MS accounts (we use Google for our email and productivity suite, so this hadn't ever been done for MS). Once this had been done, and I could use my regular email for my Teams account, I was … tada! … shown the chat option.

The Teams interface changed quite a bit. The layout of the UI and the location of buttons/options were different to the version I saw as a guest.

I hope this helps.