Sharaing of resources

Hi, together with my team we faced problem with sharing of resources on MS Teams.

Our client is an administrator and user of MS Teams within whole organisation and during project shared resources with us to make our work easier (added our work emails). However any one from my team is able to join MS Teams.
What could be the possible issue with it. (In our company we don't have license on MS Teams).
We tried accessing with client VPN, tried various net browsers.
Could you please help us with this? Thanks!!

The communicate is like: Ask your administrator to turn on MS Teams app.