Teams and SharePoint Online share a connection through the Files Channel tab. Unfortunately, if you rename the URL of a SharePoint site, the connection broke. The good news is that Microsoft has now fixed the problem. Some pesky bugs got in the way, one of which stopped the connection being restored. But the developers persisted and the final bug was fixed last week.
A reader reports that the Teams Files channel tab is only able to display 300 items from a large SharePoint folder. Three hundred seemed like an arbitrary limit, but as it turns out, the new Files channel tab fixes the problem and all will be well once Office 365 completes the deployment to get the new Files Channel tab to all tenants.
Microsoft has refreshed the Files channel tab to expose more functionality for Teams users when working with SharePoint Online document libraries.Office 365 commercial tenants should see the new UI in June 2019. The new Files channel tab is almost at feature parity with the functionality available through the SharePoint browser UI, but it still lacks the ability to expose and edit document properties.