When building your first app or bot for Microsoft Teams, one error you might come across during your development when you're using the tool ngrok is in App Studio. In the Manifest Editor, when you go to the Test and Distribute tab, if you've been following along with a tutorial, you might see an error like:

It's important to note that this is actually just a warning and not an error. This warning will not block you from proceeding to install the app in to Teams and having it function correctly (and of course, separately, to do this you need to have your development environment setup correctly including enabling custom app loading).