Heroku: Unknown response while starting app

I am trying to use turboku to connect my heroku app. After connecting my heroku account, I click the ‘deploy heroku app’ button, I then get ‘Unknown response while starting app’ error. How can I resolve this?

The Turboku feature is a convenient way to launch a Heroku app on Fly, but it doesn’t work for all Heroku apps.

Your best bet is to download flyctl and deploy manually: Speedrun! Deploying to Fly! · Fly Docs