In some organization, 3rd Party Apps are blocked in Teams. To make sure you can proceed to the SalesTim App and the Home App install you need to verify this:
Allow SalesTim App to appear to user
In this step you ensure that the allowed in the tenant:
In the teams Admin Portal go to: Manage apps - Teams admin center.
Search for SalesTim select and click "Allow"
Give the permission to user to install SalesTim
In step you make sure that the 2 SalesTim App can be installed on Teams for users.
Select the policy Global
You might find this with 3rd Party App and Custom App not allowed.
Then chose Allow Specific Apps and Block all Others
Then chose SalesTim
Then you'll have this:
Then repeat this for the Home App (assuming you already added the App as described in the Step 1 and 2 of this doc)
Now should see this:
Click on save and you're all set!