With Teams Manager, Template visibility is governed by your role within your organization.
As an Admin, there are a couple of possible causes for the issue:
You've selected a View that doesn't contain certain teams present on your tenant. Simply click the View dropdown in the top right corner and switch to the Default view to see if the teams start showing up.
You're looking for Unmanaged Teams, which are teams that were created outside of Teams Manager and thus won't show up in the app at all. You can resolve this issue by converting them into Managed Teams.
As a user, you're restricted to viewing teams that you're a part of, along with public teams. If there's a particular team that you need to access, we recommend consulting your organization's Teams Admin for more information.