Enabling app in Microsoft Teams admin canter is a way how to deliver Teams app to client application.
There are three types of Apps: Microsoft Apps, Third-Party Apps and custom apps.
Microsoft Apps – Developed by Microsoft
Third-Party Apps – Developed by third-party companies
Custom Apps – Built in-house or from some unapproved source
For user to see the app we need to check configuration on few places -manage Apps, Org-Wide app settings, Permission Policies and Setup Policies. But in this case it is a MS App so we need to check only two places if there is no need to ping the app to the users.

In-Org Wide app settings you can configure interaction with third party and custom apps which we wont touch in this example as we are adding Microsoft app – Microsoft Lists.
First let’s check if the app is blocked or allowed in Manage Apps settings:

First test passed – App is allowed on a tenant level. But this still does not mean that all users are able access the app.
Next thing that we want to check is Permission Policies – We will check “Global (Org-wide default)” as we want to enable the app for all users by default.
As this is Microsoft App we are checking the set-up of a “Microsoft App” setting.

I did not find Microsoft Lists App on the lists do this is the place I need to add the app.

Seup Policies we do not need to touch for this example because we already have the setup that we wanted.
After deleting cache I am aple to see MS Lists in my Teams client app:
