Why is my Microsoft Teams Messaging Extension only available in a 1:1 chat?

My MS Teams Messaging Extension only works in a 1:1 chat but should also work in a group chat as well as in a Teams Chat. My App wont show as installed while in group or Teams chats but can be used as intended in a 1:1 chat.

I use a developer environment which gives me a preconfigured teams with demo users and other stuff
I’ve used an App Registration in Azure and called the https://login.microsoftonline.com/{{id}}/oauth2/token endpoint from graph to get my token which I use in the teamsBot.js file (see code below)

I created a messaging extension for Microsoft Teams and used the Teams Toolkit Messaging Extension in VS Code for the initial setup.

All I did so far is update the async handleTeamsMessagingExtensionQuery(context, query) function to use axios to call the MS Graph API to access a SharePoint Document Library

const thumbnail = await axios.get(`https://graph.microsoft.com/v1.0/sites/{{siteId}}/drives/{{driveId}}/items/{{itemId}}/thumbnails`,
      {
        headers: {
          Authorization: "Bearer {{token}}"
        }
      })

And changed the preview Card to CardFactory.thumbnailCard().

My Question(s):

1. Why is my Extension only available in a 1:1 chat and not in a Teams Chat or a group Chat?
2. Is it possible to enable it for all chats?