Using 2 instances of Teams

TomArbuthnot Thanks so much for the reply.

My main account is my company A.  I have a separate guest account at company B, using a new email address provided by that company.

Here's the screenshot of accessing company B in the Teams desktop app.  Notice for the the team I'm accessing here I can see the General, Posts, Files and Wiki sections:

Now, using that same logon to the web app, that team is not listed:

Hopefully, I'm missing something obvious.