Microsoft Teams sites are by default set to be private. This improves security by ensuring files stored in a Team can only be accessed by members of that Team. In some cases, you may run into a situation where you need to make specific files stored in a Team available to non-team members or to create a link to a file so anyone with the link can access it (e.g. if you need to make a video available on a web page). You can request a specific Team site be opened up for this functionality by opening a support ticket.
Opening a support ticket