ERR_NGROK_447: Managed certificates are not allowed on direct subdomains of DOMAIN

What does ERR_NGROK_447 mean?

ngrok returns ERR_NGROK_447 with this message:

Managed certificates are not allowed on direct subdomains of <DOMAIN>.

Troubleshoot ERR_NGROK_447 with your AI agent. Connect it to the ngrok MCP server, then ask what caused the error and how to fix it.

Email support@ngrok.com and include the error code.