Only paid plans may bind custom subdomains.
Failed to bind the custom subdomain subdomain for an unauthenticated client.
Sign up at: https://dashboard.ngrok.com/signup
If you have already signed up, make sure your authtoken is installed.
Your authtoken is available on your dashboard: https://dashboard.ngrok.com/get-started/your-authtoken
Binding a custom subdomain on the ngrok.io domain requires a paid plan. Once you sign up for a paid plan, we'll give you an authtoken that you'll add to your ngrok agent. This will allow you to use custom subdomains.
Sign up for a paid plan at https://dashboard.ngrok.com/signup You'll need the Basic plan or better.
Add the authtoken from your account dashboard to your ngrok agent in your terminal.
If you're having trouble resolving this error, please reach out to support@ngrok.com.